Mitotic divisions hi-res stock photography and images

Different stages of mitosis: prophase, metaphase, anaphase, telophase, interphase. Stock Photo

RF2JKWN7M–Different stages of mitosis: prophase, metaphase, anaphase, telophase, interphase.

Archive image from page 54 of Cunningham's Text-book of anatomy (1914). Cunningham's Text-book of anatomy cunninghamstextb00cunn Year: 1914 ( Fig. 24. Segmentation of Zygote. 2-Cell Stage. Polar bodies Oolemma Fig. 25.- -Segmentatk in i if Zygote. 4-Cell Stage. Segmentation. Immediately after its formation the zygote is separated, by a series of consecu- tive mitotic divisions, into a large number of cells which are grouped together in the form of a solid spherical mass, called a morula on account of the mulberry- like appearance of its surface. This period of division is called the period Stock Photo

RMW9FMF7–Archive image from page 54 of Cunningham's Text-book of anatomy (1914). Cunningham's Text-book of anatomy cunninghamstextb00cunn Year: 1914 ( Fig. 24. Segmentation of Zygote. 2-Cell Stage. Polar bodies Oolemma Fig. 25.- -Segmentatk in i if Zygote. 4-Cell Stage. Segmentation. Immediately after its formation the zygote is separated, by a series of consecu- tive mitotic divisions, into a large number of cells which are grouped together in the form of a solid spherical mass, called a morula on account of the mulberry- like appearance of its surface. This period of division is called the period

RMCT58TJ–MITOSIS

. The American journal of anatomy . Fig. 17 Lymphatic sprout from the hyla pickeringii larva on which studiesin figs. 1 to 14 were made, showing mitotic division of a nucleus. This divisiontook place on May 5, while the larva was anesthetized with chloretone. The num-bers show the time. From 9:18 to 9:44 inclusive, the dividing nuclear area aloneis shown. Enlarged approximately 450 times. 378 ELIOT R. CLARK they gradually resume the character of the non-dividing nuclearareas. During the division the wall of the lymphatic remainscontinuous. Mitotic divisions have been observed in the main cauda Stock Photo

RM2CH9HY6–. The American journal of anatomy . Fig. 17 Lymphatic sprout from the hyla pickeringii larva on which studiesin figs. 1 to 14 were made, showing mitotic division of a nucleus. This divisiontook place on May 5, while the larva was anesthetized with chloretone. The num-bers show the time. From 9:18 to 9:44 inclusive, the dividing nuclear area aloneis shown. Enlarged approximately 450 times. 378 ELIOT R. CLARK they gradually resume the character of the non-dividing nuclearareas. During the division the wall of the lymphatic remainscontinuous. Mitotic divisions have been observed in the main cauda

RM2AJ9TJK–Oral anticancer agents

. Morphology of gymnosperms. Gymnosperms; Plant morphology. 394 MORPHOLOGY OF GYMNOSPERMS before the walls disappear the jacket cells become binucleate, the nuclei dividing mitotically and amitotically. Mitotic divisions may- occur simultaneously in every cell of both layers of the jacket, or every division may be amitotic, or both kinds of division may occur in the same jacket. Amitotic divisions occurring at the upper end of the archegonium might pass easily for fusions. In some jacket cells the. Please note that these images are extracted from scanned page images that may have been digitall Stock Photo

RMPG2JAM–. Morphology of gymnosperms. Gymnosperms; Plant morphology. 394 MORPHOLOGY OF GYMNOSPERMS before the walls disappear the jacket cells become binucleate, the nuclei dividing mitotically and amitotically. Mitotic divisions may- occur simultaneously in every cell of both layers of the jacket, or every division may be amitotic, or both kinds of division may occur in the same jacket. Amitotic divisions occurring at the upper end of the archegonium might pass easily for fusions. In some jacket cells the. Please note that these images are extracted from scanned page images that may have been digitall

. The physical basis of heredity . rads, a; egg with first polar spindle, b;egg after extrusion of first polar body, c; egg with second polar spindle, d; egg after theextrusion of both polar bodies, c. to one pole and half to the other (Fig. 15, d). A sec-ond protrusion takes place from the surface of the eggwhich pinches off to form the second polar body (Fig.15, e). Thus, after two mitotic divisions, the egg has lostthree-quarters of its chromatin, but retains half the full MECHANISM IN SEGREGATION 41 number of chromosomes, and as a result, the originaltwelve chromosomes have been reduced to Stock Photo

RM2CHRF6D–. The physical basis of heredity . rads, a; egg with first polar spindle, b;egg after extrusion of first polar body, c; egg with second polar spindle, d; egg after theextrusion of both polar bodies, c. to one pole and half to the other (Fig. 15, d). A sec-ond protrusion takes place from the surface of the eggwhich pinches off to form the second polar body (Fig.15, e). Thus, after two mitotic divisions, the egg has lostthree-quarters of its chromatin, but retains half the full MECHANISM IN SEGREGATION 41 number of chromosomes, and as a result, the originaltwelve chromosomes have been reduced to

RM2AJ9XJG–Chemotherapy

. Cunningham's Text-book of anatomy. Anatomy. Fig. 25.- -Segmentatk in i if Zygote. 4-Cell Stage. Segmentation. Immediately after its formation the zygote is separated, by a series of consecu- tive mitotic divisions, into a large number of cells which are grouped together in the form of a solid spherical mass, called a morula on account of the mulberry- like appearance of its surface. This period of division is called the period of segmentation (Figs. 24-27). The segmentation divisions are of the homotype form, and there is evidence which tends to the con- clusion that the earliest divisions, Stock Photo

RMPFTYC4–. Cunningham's Text-book of anatomy. Anatomy. Fig. 25.- -Segmentatk in i if Zygote. 4-Cell Stage. Segmentation. Immediately after its formation the zygote is separated, by a series of consecu- tive mitotic divisions, into a large number of cells which are grouped together in the form of a solid spherical mass, called a morula on account of the mulberry- like appearance of its surface. This period of division is called the period of segmentation (Figs. 24-27). The segmentation divisions are of the homotype form, and there is evidence which tends to the con- clusion that the earliest divisions,

RMRDH5WR–. Morphology of gymnosperms. Gymnosperms; Plant morphology. 394 MORPHOLOGY OF GYMNOSPERMS before the walls disappear the jacket cells become binucleate, the nuclei dividing mitotically and amitotically. Mitotic divisions may- occur simultaneously in every cell of both layers of the jacket, or every division may be amitotic, or both kinds of division may occur in the same jacket. Amitotic divisions occurring at the upper end of the archegonium might pass easily for fusions. In some jacket cells the. Please note that these images are extracted from scanned page images that may have been digitall

RM2AJ9XJT–Chemotherapy

. Cunningham's Text-book of anatomy. Anatomy. Fig. 24. Segmentation of Zygote. 2-Cell Stage. Polar bodies Oolemma. Fig. 25.- -Segmentatk in i if Zygote. 4-Cell Stage. Segmentation. Immediately after its formation the zygote is separated, by a series of consecu- tive mitotic divisions, into a large number of cells which are grouped together in the form of a solid spherical mass, called a morula on account of the mulberry- like appearance of its surface. This period of division is called the period of segmentation (Figs. 24-27). The segmentation divisions are of the homotype form, and there is e Stock Photo

RMPFTYCH–. Cunningham's Text-book of anatomy. Anatomy. Fig. 24. Segmentation of Zygote. 2-Cell Stage. Polar bodies Oolemma. Fig. 25.- -Segmentatk in i if Zygote. 4-Cell Stage. Segmentation. Immediately after its formation the zygote is separated, by a series of consecu- tive mitotic divisions, into a large number of cells which are grouped together in the form of a solid spherical mass, called a morula on account of the mulberry- like appearance of its surface. This period of division is called the period of segmentation (Figs. 24-27). The segmentation divisions are of the homotype form, and there is e

. Text-book of embryology. Embryology. SEGMENTATION 13 in an egg in which the proportion of yolk.present approaches the maximum. In this case the zygote nucleus commonly undergoes two mitotic divisions before there is any external symptom of segmentation of the cytoplasm. Usually a single furrow makes its appearance first, incising the surface of the germinal disc but not extending to its periphery (Fig. 8, A). Occasionally a second regular furrow makes its appearance intersecting the first at right angles. Fig. 7.—Vertical (meridional) sections through blastulae of Frog. (From Morgan, 1897.) Stock Photo

RMRDJA8H–. Text-book of embryology. Embryology. SEGMENTATION 13 in an egg in which the proportion of yolk.present approaches the maximum. In this case the zygote nucleus commonly undergoes two mitotic divisions before there is any external symptom of segmentation of the cytoplasm. Usually a single furrow makes its appearance first, incising the surface of the germinal disc but not extending to its periphery (Fig. 8, A). Occasionally a second regular furrow makes its appearance intersecting the first at right angles. Fig. 7.—Vertical (meridional) sections through blastulae of Frog. (From Morgan, 1897.)

RM2AJ9XJ8–Chemotherapy

. Morphology of gymnosperms. Gymnosperms; Plant morphology. 152 MORPHOLOGY OF GYMNOSPERMS After fertilization there is a prolonged period of free nuclear divi- sion, in which the mitotic figures are intranuclear and the spindles very conspicuous (fig. 178). Since some have regarded the blepharoplast as a centrosome, these figures have been examined with great care, and it can be stated confidently that no centrosomes are concerned in their formation. The free nuclear divisions are simultaneous, just as in the germination of the megaspore or in the early development of endosperm in most angiosp Stock Photo

RMPG2K9M–. Morphology of gymnosperms. Gymnosperms; Plant morphology. 152 MORPHOLOGY OF GYMNOSPERMS After fertilization there is a prolonged period of free nuclear divi- sion, in which the mitotic figures are intranuclear and the spindles very conspicuous (fig. 178). Since some have regarded the blepharoplast as a centrosome, these figures have been examined with great care, and it can be stated confidently that no centrosomes are concerned in their formation. The free nuclear divisions are simultaneous, just as in the germination of the megaspore or in the early development of endosperm in most angiosp

RMRD6KAD–. Cunningham's Text-book of anatomy. Anatomy. Fig. 25.- -Segmentatk in i if Zygote. 4-Cell Stage. Segmentation. Immediately after its formation the zygote is separated, by a series of consecu- tive mitotic divisions, into a large number of cells which are grouped together in the form of a solid spherical mass, called a morula on account of the mulberry- like appearance of its surface. This period of division is called the period of segmentation (Figs. 24-27). The segmentation divisions are of the homotype form, and there is evidence which tends to the con- clusion that the earliest divisions,

RM2AJ9XJR–Chemotherapy

RMCPNHB0–MITOSIS

. The biology of hydra and of some other coelenterates, 1961. Hydra; Cnidaria; Ctenophora; Cnidaria; Hydra. .-/ji Fig. 1. Intercellular bridge of interstitial cells. counters the spindle remnant, and is arrested by it for a time. This occurs very commonly in mitotic divisions in many kinds of genninal and somatic cells and gives rise to a transient structure called a spindle bridge. Usually, however, such connections between the daughter cells endure only for several minutes and then when the spindle remnants have resorbed the cleavage is completed. Evi- dently in the case being described here Stock Photo

RMRHK65G–. The biology of hydra and of some other coelenterates, 1961. Hydra; Cnidaria; Ctenophora; Cnidaria; Hydra. .-/ji Fig. 1. Intercellular bridge of interstitial cells. counters the spindle remnant, and is arrested by it for a time. This occurs very commonly in mitotic divisions in many kinds of genninal and somatic cells and gives rise to a transient structure called a spindle bridge. Usually, however, such connections between the daughter cells endure only for several minutes and then when the spindle remnants have resorbed the cleavage is completed. Evi- dently in the case being described here

RMCPNHBE–CANCER CELL, ILLUSTRATION

RMCRYCED–EMBRYO, ILLUSTRATION

RMCRYY9T–EMBRYO, ILLUSTRATION

RMCRYCE8–EMBRYO, ILLUSTRATION

RMCRYYTF–EMBRYO, ILLUSTRATION

RMCRYHBP–MITOSIS TELOPHASE

RMRD6KAM–. Cunningham's Text-book of anatomy. Anatomy. Fig. 24. Segmentation of Zygote. 2-Cell Stage. Polar bodies Oolemma. Fig. 25.- -Segmentatk in i if Zygote. 4-Cell Stage. Segmentation. Immediately after its formation the zygote is separated, by a series of consecu- tive mitotic divisions, into a large number of cells which are grouped together in the form of a solid spherical mass, called a morula on account of the mulberry- like appearance of its surface. This period of division is called the period of segmentation (Figs. 24-27). The segmentation divisions are of the homotype form, and there is e

RMCRYHC4–MITOSIS ANAPHASE

. The Biological bulletin. Biology; Zoology; Marine biology. 146 CLARENCE D. TURNER are partly closed by a loose syncytium, the interspaces of which often contain degenerating cells. No spermatids or spermatozoa are present and mitotic divisions are seldom encountered (Fig. 3). Many degen- erating epithelial cells with pycnotic nuclei are present throughout the. Fig. 1. An involuted testis from a control. Bouin-hematoxylin. X 55. Fig. 2. An involuted testis subsequent to 30-day treatment with Antuitrin-S (total 600 r. u.). Bouin-hematoxylin. X 55. Fig. 3. Higher magnification of a portion of F Stock Photo

RMRHKJ39–. The Biological bulletin. Biology; Zoology; Marine biology. 146 CLARENCE D. TURNER are partly closed by a loose syncytium, the interspaces of which often contain degenerating cells. No spermatids or spermatozoa are present and mitotic divisions are seldom encountered (Fig. 3). Many degen- erating epithelial cells with pycnotic nuclei are present throughout the. Fig. 1. An involuted testis from a control. Bouin-hematoxylin. X 55. Fig. 2. An involuted testis subsequent to 30-day treatment with Antuitrin-S (total 600 r. u.). Bouin-hematoxylin. X 55. Fig. 3. Higher magnification of a portion of F

RMCRYHBD–MITOSIS METAPHASE

. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. FIG. 9. Resting oogonium with a definite chromatin reticulum ; no " Nebendot- ter " present. FIG. 10. Oogonium ; very early prophase, spireme formation beginning. FIGS. 9-17. From cells stained with Kernschwarz and Lichtgriin. the divisions. It is well known that physiological factors may govern the time of mitotic divisions. A case in point is that recently described by Beckwith, previously mentioned ; likewise, in certain insects and in many plants mitosis occurs at night only. The fact that many nuclei from one Stock Photo

RMRHRK5H–. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. FIG. 9. Resting oogonium with a definite chromatin reticulum ; no " Nebendot- ter " present. FIG. 10. Oogonium ; very early prophase, spireme formation beginning. FIGS. 9-17. From cells stained with Kernschwarz and Lichtgriin. the divisions. It is well known that physiological factors may govern the time of mitotic divisions. A case in point is that recently described by Beckwith, previously mentioned ; likewise, in certain insects and in many plants mitosis occurs at night only. The fact that many nuclei from one

RMCRYHBY–MITOSIS ANAPHASE

. Animal growth and development. Embryology; Growth; Biology; Growth; Embryology; Animals -- growth & development. Adult cap Resting cyst Fig. 10. Life cycle of Ace- fabularia med'iferranea (after Brachet, Biochemical Cytology, p. 303). In the laboratory, unlike in the natural habitat, develop- ment of the adult structure from the zygote is direct, without regression, and takes only one year. Germinating cyst. '^0 Nucleus Zygote 2 days to yield haploid daughter nuclei. Subsequent mitotic divisions produce a great number of tiny haploid nuclei that stream away from the rhizoid into the cap Stock Photo

RMRN5WDA–. Animal growth and development. Embryology; Growth; Biology; Growth; Embryology; Animals -- growth & development. Adult cap Resting cyst Fig. 10. Life cycle of Ace- fabularia med'iferranea (after Brachet, Biochemical Cytology, p. 303). In the laboratory, unlike in the natural habitat, develop- ment of the adult structure from the zygote is direct, without regression, and takes only one year. Germinating cyst. '^0 Nucleus Zygote 2 days to yield haploid daughter nuclei. Subsequent mitotic divisions produce a great number of tiny haploid nuclei that stream away from the rhizoid into the cap

. Carnegie Institution of Washington publication. 74 FECUNDATION ; NON-MOTILE ISOGAMETES. in general two pyrenoids, undergoes a rejuvenescence and finally divides. Prior to this cell-division, however, two successive mitotic divisions of the nucleus1 take place (Fig. 22, A to E). After the first mitosis the daughter nuclei generally move apart toward the ends of the cell whither the pyrenoids also wander (Fig. 22, B). Soon the second mitosis takes place, when four nuclei similar in appearance are present in the protoplast, which may, as yet, show no sign of division (Fig. 22, D). With further Stock Photo

RMRFWC6J–. Carnegie Institution of Washington publication. 74 FECUNDATION ; NON-MOTILE ISOGAMETES. in general two pyrenoids, undergoes a rejuvenescence and finally divides. Prior to this cell-division, however, two successive mitotic divisions of the nucleus1 take place (Fig. 22, A to E). After the first mitosis the daughter nuclei generally move apart toward the ends of the cell whither the pyrenoids also wander (Fig. 22, B). Soon the second mitosis takes place, when four nuclei similar in appearance are present in the protoplast, which may, as yet, show no sign of division (Fig. 22, D). With further

. The Biological bulletin. Biology; Zoology; Marine biology. 134 GEORGE FRED SUTHERLAND. 10 (six days' regeneration) shows the cells in one part of the cord stretched out to such an extent that vacuoles are left between the. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Fig. 12. Curve giving the number of mitotic divisions in that part of the spinal cord within 3 mm. of the edge. Beyond 3 mm. the mitoses are scattered. An abscissa represents the period of regeneration and the corresponding ordinate gives the average number of mitoses found in the individuals killed at the end of that period. cells. I Stock Photo

RMRHG8WG–. The Biological bulletin. Biology; Zoology; Marine biology. 134 GEORGE FRED SUTHERLAND. 10 (six days' regeneration) shows the cells in one part of the cord stretched out to such an extent that vacuoles are left between the. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Fig. 12. Curve giving the number of mitotic divisions in that part of the spinal cord within 3 mm. of the edge. Beyond 3 mm. the mitoses are scattered. An abscissa represents the period of regeneration and the corresponding ordinate gives the average number of mitoses found in the individuals killed at the end of that period. cells. I

The cell in development and inheritance . en in carcinoma, maybe artificially produced in the epithelial cells of salamanders (Fig. 47)by treatment with dilute solutions of various drugs (antipyrin, cocaine,quinine). DETAILS OF MITOSIS 99 Normal multipolar mitoses, though rare, sometimes occur, as in thedivision of the pollen-mother-cells and the endosperm-cells of flower-ing plants (Strasburger); but such mitotic figures arise through theunion of two or more bipolar amphiasters in a syncytium and aredue to a rapid succession of the nuclear divisions unaccompanied byfission of the cell-substan Stock Photo

RM2AJGEMC–The cell in development and inheritance . en in carcinoma, maybe artificially produced in the epithelial cells of salamanders (Fig. 47)by treatment with dilute solutions of various drugs (antipyrin, cocaine,quinine). DETAILS OF MITOSIS 99 Normal multipolar mitoses, though rare, sometimes occur, as in thedivision of the pollen-mother-cells and the endosperm-cells of flower-ing plants (Strasburger); but such mitotic figures arise through theunion of two or more bipolar amphiasters in a syncytium and aredue to a rapid succession of the nuclear divisions unaccompanied byfission of the cell-substan

Induced cell-reproduction and cancer.. . be inducedby this fresh extract alone in the experimental tenminutes. The best jelly to make in order to causesuprarenal extract to induce divisions in lymphocytesin the ten minutes is: 5 cc. of coefficient jelly, 1 cc. ofalkali solution, 2 cc. of a 10-per-cent solution of driedsuprarenal extract, and 2 cc. of water. By means ofthis jelly advanced mitotic figures can be induced inlymphocytes. So it was proved, therefore, that this extract of deadsuprarenal gland contains a substance which will causethe divisions of lymphocytes. A fresh jelly was thenpre Stock Photo

RM2AJ27Y3–Induced cell-reproduction and cancer.. . be inducedby this fresh extract alone in the experimental tenminutes. The best jelly to make in order to causesuprarenal extract to induce divisions in lymphocytesin the ten minutes is: 5 cc. of coefficient jelly, 1 cc. ofalkali solution, 2 cc. of a 10-per-cent solution of driedsuprarenal extract, and 2 cc. of water. By means ofthis jelly advanced mitotic figures can be induced inlymphocytes. So it was proved, therefore, that this extract of deadsuprarenal gland contains a substance which will causethe divisions of lymphocytes. A fresh jelly was thenpre

. The structure and development of crown gall : a plant cancer . THE STROMA. Pari passu with the growth of the tumor cells new supportingtissues are developed in the tumor in various places. These supporting. Fig. 1.—Nuclear divisions in crown gall: Nos. 1 to 16, cells showing stages of amitotic division; No. 17,mitotic division in which, more chromosomes have passed to one pole than to the other. Material fixedin Flemming, and stained with Heidenhains iron hsematoxylin. tissues consist of pitted vessels and wood fibers, but frequently thelatter are scanty or absent. Sieve tubes are also prese Stock Photo

RM2CDEWJ4–. The structure and development of crown gall : a plant cancer . THE STROMA. Pari passu with the growth of the tumor cells new supportingtissues are developed in the tumor in various places. These supporting. Fig. 1.—Nuclear divisions in crown gall: Nos. 1 to 16, cells showing stages of amitotic division; No. 17,mitotic division in which, more chromosomes have passed to one pole than to the other. Material fixedin Flemming, and stained with Heidenhains iron hsematoxylin. tissues consist of pitted vessels and wood fibers, but frequently thelatter are scanty or absent. Sieve tubes are also prese

. Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching. Embryology -- Insects; Embryology -- Myriapoda. ORTHOPTEROIDEA (PANORTHOPTERA) 223 [leriphery. At about 10 hours, after several divisions, the eggs being maintained at a constant temperature of 33°C., the cleavage cells start migration to the periphery, which they reach by the 18-hour stage. Meanwhile with repeated mitotic divisions there is an anterior migration along the periphery of the egg but not through the yolk. About the twenty-third hour the cel Stock Photo

RMRC5KEH–. Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching. Embryology -- Insects; Embryology -- Myriapoda. ORTHOPTEROIDEA (PANORTHOPTERA) 223 [leriphery. At about 10 hours, after several divisions, the eggs being maintained at a constant temperature of 33°C., the cleavage cells start migration to the periphery, which they reach by the 18-hour stage. Meanwhile with repeated mitotic divisions there is an anterior migration along the periphery of the egg but not through the yolk. About the twenty-third hour the cel

RMRDH6MW–. Morphology of gymnosperms. Gymnosperms; Plant morphology. 152 MORPHOLOGY OF GYMNOSPERMS After fertilization there is a prolonged period of free nuclear divi- sion, in which the mitotic figures are intranuclear and the spindles very conspicuous (fig. 178). Since some have regarded the blepharoplast as a centrosome, these figures have been examined with great care, and it can be stated confidently that no centrosomes are concerned in their formation. The free nuclear divisions are simultaneous, just as in the germination of the megaspore or in the early development of endosperm in most angiosp

. Protozoo?logy. Protozoa; Protozoa, Pathogenic. FERTILIZATION BY ENDOGAMY 149 nuclei remaining (from one to twenty). Each of these daughter cysts secretes a gelatinous envelope about itself, and the nucleus of each divides by mitosis. This mitotic division is followed by division of the cytospore into two daughter cells (cytospores No. 2), and in these there are two successive nuclear divisions resulting in four nuclei. Three of these nuclei degenerate ("polar bodies") and one remains as a pronucleus. The cytospores of the second order next unite again, reforming the cytospores No. Stock Photo

RMRDXM58–. Protozoo?logy. Protozoa; Protozoa, Pathogenic. FERTILIZATION BY ENDOGAMY 149 nuclei remaining (from one to twenty). Each of these daughter cysts secretes a gelatinous envelope about itself, and the nucleus of each divides by mitosis. This mitotic division is followed by division of the cytospore into two daughter cells (cytospores No. 2), and in these there are two successive nuclear divisions resulting in four nuclei. Three of these nuclei degenerate ("polar bodies") and one remains as a pronucleus. The cytospores of the second order next unite again, reforming the cytospores No.

. The cell in development and inheritance. Cells. DETAILS OF MITOSIS 99 Normal multipolar mitoses, though rare, sometimes occu'-,'as in the division of the pollen-mother-cells and the endosperm-cells of flower- ing plants (Strasburger); but such mitotic figures arise through the union of two or more bipolar amphiasters in a syncytium and are due to a rapid succession of the nuclear divisions unaccompanied by fission of the cell-substance. These are not to be confounded with pathological mitoses arising by premature or abnormal division of the centrosome. If one centrosome divide, while the oth Stock Photo

RMRJD45B–. The cell in development and inheritance. Cells. DETAILS OF MITOSIS 99 Normal multipolar mitoses, though rare, sometimes occu'-,'as in the division of the pollen-mother-cells and the endosperm-cells of flower- ing plants (Strasburger); but such mitotic figures arise through the union of two or more bipolar amphiasters in a syncytium and are due to a rapid succession of the nuclear divisions unaccompanied by fission of the cell-substance. These are not to be confounded with pathological mitoses arising by premature or abnormal division of the centrosome. If one centrosome divide, while the oth

. The cell in development and inheritance. Cells. DETAILS OF MITOSIS 99 Normal multipolar mitoses, though rare, sometimes occur, as in the division of the pollen-mother-cells and the endosperm-cells of flower- ing plants (Strasburger); but such mitotic figures arise through the union of two or more bipolar amphiasters in a syncytium and are due to a rapid succession of the nuclear divisions unaccompanied by fission of the cell-substance. These are not to be confounded with pathological mitoses arising by premature or abnormal division of the centrosome. If one centrosome divide, while the othe Stock Photo

RMRJDWH2–. The cell in development and inheritance. Cells. DETAILS OF MITOSIS 99 Normal multipolar mitoses, though rare, sometimes occur, as in the division of the pollen-mother-cells and the endosperm-cells of flower- ing plants (Strasburger); but such mitotic figures arise through the union of two or more bipolar amphiasters in a syncytium and are due to a rapid succession of the nuclear divisions unaccompanied by fission of the cell-substance. These are not to be confounded with pathological mitoses arising by premature or abnormal division of the centrosome. If one centrosome divide, while the othe

. The plant cell, its modifications and vital processes; a manual for students. Plant physiology; Plant anatomy; Plant cells and tissues. 130 THE PLANT CELL. Note.—The study of the development of the microspore may be readily carried out in sections of the young flower of Polygonatum. Longi- tudinal sections of the fixed and hardened flower buds will out across the young anthers. Sections should be stained with safranin and hsematoxylin to show up the mitotic figures in the divisions of the pollen mother-cells. The study of the maturation of the microspore is difficult to carry out, and rather Stock Photo

RMRDYC6B–. The plant cell, its modifications and vital processes; a manual for students. Plant physiology; Plant anatomy; Plant cells and tissues. 130 THE PLANT CELL. Note.—The study of the development of the microspore may be readily carried out in sections of the young flower of Polygonatum. Longi- tudinal sections of the fixed and hardened flower buds will out across the young anthers. Sections should be stained with safranin and hsematoxylin to show up the mitotic figures in the divisions of the pollen mother-cells. The study of the maturation of the microspore is difficult to carry out, and rather

. The botanical magazine = Shokubutsugaku zasshi. Plants; Botany. Aug.. 1922.] SINOTOO—OENOTHERA LAMARCKIANA. 93 were cut 5—20 {iin thickness for the study of mitotic figures, and 60?120 fJL for counting the pollen grains. For the germination test of the seeds the method described by Davis(2) was adopted. Abnormal behaviors of chromosomes in the meiotic divisions According to former investigators of the Oenothera cytology, the meiotic chromosomes, especially in the heterotypic division, are loosely paired and the regular nuclear plates are rarely found. It seems to the writer, however, that th Stock Photo

RMRHB1GA–. The botanical magazine = Shokubutsugaku zasshi. Plants; Botany. Aug.. 1922.] SINOTOO—OENOTHERA LAMARCKIANA. 93 were cut 5—20 {iin thickness for the study of mitotic figures, and 60?120 fJL for counting the pollen grains. For the germination test of the seeds the method described by Davis(2) was adopted. Abnormal behaviors of chromosomes in the meiotic divisions According to former investigators of the Oenothera cytology, the meiotic chromosomes, especially in the heterotypic division, are loosely paired and the regular nuclear plates are rarely found. It seems to the writer, however, that th

. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CLEAVAGE AXD YOLK FORMATION IX TISBE 337 the later growth of the eggs the platelets increase only in number but not in size (Fig. 2). After fertilization the characteristic double nuclei form (Fig. 3) and the first cleavage divisions are distinguished by the formation of double spindles and the maintenance of separate paternal and maternal groups of chromosomes (Fig. 4). During the mitotic. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration Stock Photo

RMRHP9YC–. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CLEAVAGE AXD YOLK FORMATION IX TISBE 337 the later growth of the eggs the platelets increase only in number but not in size (Fig. 2). After fertilization the characteristic double nuclei form (Fig. 3) and the first cleavage divisions are distinguished by the formation of double spindles and the maintenance of separate paternal and maternal groups of chromosomes (Fig. 4). During the mitotic. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration

. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MITOTIC RHYTHMS IN THE EUGLENINEAE 167 culture in any conditions or intensity of artificial lighting, either direct or diffused, incandescent or fluorescent. Attempts to reverse the mitotic periodicity in a tem- perature-controlled cabinet with lighting on a time-switch were unsuccessful, the cells becoming quiescent with no divisions occurring. Similarly, no mitosis occurred in either continuous light or continuous darkness. Returned to natural light con- ditions after such treatment, the cells recovered their full division Stock Photo

RMRHMNE2–. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MITOTIC RHYTHMS IN THE EUGLENINEAE 167 culture in any conditions or intensity of artificial lighting, either direct or diffused, incandescent or fluorescent. Attempts to reverse the mitotic periodicity in a tem- perature-controlled cabinet with lighting on a time-switch were unsuccessful, the cells becoming quiescent with no divisions occurring. Similarly, no mitosis occurred in either continuous light or continuous darkness. Returned to natural light con- ditions after such treatment, the cells recovered their full division

. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 314 W. R. COE appeanmcr. with a delicate spindle of the usual form. The chromosome numlKT could not be definitely determined because of the crowded con- dition of tlu- metapha.se and anaphase plates, hut it is not very large. There arc two typical spermatocyte divisions. Si-coinlury spcrniatocytes.—The secondary spermatocytcs arc like- wise hi'ld together in a crowded, spherical mass. Nuclear behavior and mitotic figures do not deviate from the typical condition (Figs. 2, 4). Spermatids.—These also remain in close contact an Stock Photo

RMRHP6B3–. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 314 W. R. COE appeanmcr. with a delicate spindle of the usual form. The chromosome numlKT could not be definitely determined because of the crowded con- dition of tlu- metapha.se and anaphase plates, hut it is not very large. There arc two typical spermatocyte divisions. Si-coinlury spcrniatocytes.—The secondary spermatocytcs arc like- wise hi'ld together in a crowded, spherical mass. Nuclear behavior and mitotic figures do not deviate from the typical condition (Figs. 2, 4). Spermatids.—These also remain in close contact an

. Analysis of development. Embryology; Embryology. Nervous System GROWTH PATTERNS Proliferative Sources. In the ganglia, cell division is rather ubiquitous. In the CNS, on the other hand, mitoses are, in post-neurula- tion stages, confined to the inner surface, lining central canal and brain ventricles (Fig. 1J9). More peripheral layers are es- sentially devoid of mitotic figures; the ceils there continue to grow in size, but without ensuing divisions. Whether the inner "ger- minal" layer is subject to some active mito- genic stimulation by its exposure to the lumen, or rather divisi Stock Photo

RMRNAG9N–. Analysis of development. Embryology; Embryology. Nervous System GROWTH PATTERNS Proliferative Sources. In the ganglia, cell division is rather ubiquitous. In the CNS, on the other hand, mitoses are, in post-neurula- tion stages, confined to the inner surface, lining central canal and brain ventricles (Fig. 1J9). More peripheral layers are es- sentially devoid of mitotic figures; the ceils there continue to grow in size, but without ensuing divisions. Whether the inner "ger- minal" layer is subject to some active mito- genic stimulation by its exposure to the lumen, or rather divisi

. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 644 P. ROE. FIGURE 1. a. Polar body formation in egg of control Carcinonemertes epialti. Chromosomes nearest edge of the cell are those of the polar body. Some cells showed 12, other cells showed 13 chromosomes during meiotic divisions. Magnification: 1500X. b. Chromosomes in mitotic anaphase during division from one to two cell stage in embryo of control Carcinonemertes errans. The small dark spots to the left of the chromosomes are remains of chromosomes in the two polar bodies. Magnification: 1000X. c. Chromo- somes in mi Stock Photo

RMRHMXG5–. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 644 P. ROE. FIGURE 1. a. Polar body formation in egg of control Carcinonemertes epialti. Chromosomes nearest edge of the cell are those of the polar body. Some cells showed 12, other cells showed 13 chromosomes during meiotic divisions. Magnification: 1500X. b. Chromosomes in mitotic anaphase during division from one to two cell stage in embryo of control Carcinonemertes errans. The small dark spots to the left of the chromosomes are remains of chromosomes in the two polar bodies. Magnification: 1000X. c. Chromo- somes in mi

. Morphology of angiosperms (Morphology of spermatophytes. Part II). Angiosperms; Plant morphology. A. D G H / Fig, 54.—Fritillaria persica. Sections showing the two nuclear divisions by which four microspores are formed in the mother-cell by the successive (bilateral) method; x 530. A, very young mother-cell; B, nucleus in synapsis; C, 12 chromosomes, one of them rather indistinct, within the nucleus; D, mitotic figure of the first division showing the short, thick chromosomes characteristic of the reduction division; E, later stage of first division, showing vertical view of the 12 chromo- s Stock Photo

RMRDYJ67–. Morphology of angiosperms (Morphology of spermatophytes. Part II). Angiosperms; Plant morphology. A. D G H / Fig, 54.—Fritillaria persica. Sections showing the two nuclear divisions by which four microspores are formed in the mother-cell by the successive (bilateral) method; x 530. A, very young mother-cell; B, nucleus in synapsis; C, 12 chromosomes, one of them rather indistinct, within the nucleus; D, mitotic figure of the first division showing the short, thick chromosomes characteristic of the reduction division; E, later stage of first division, showing vertical view of the 12 chromo- s

. Colchicine in agriculture, medicine, biology, and chemistry. Colchicine; Colchicine. Experimental Growth in Animals 221 9.3 gives the results, with the percentages of dividing cells and of mitotic stages in control and colchicinized aninials.'^'^ From these results, it is apparent that mitotic arrest at metaphase has increased in six hours the number of cell divisions by 17.63/3.32. The mitotic duration, calculated as indicated in Section 9.2, is 3.32 X 6-0/17.63 = 1.13 = 1 hr. 8 min. It can be calculated from this result that in 37.7 hours (1.57 days), 100 per cent of the cells will have di Stock Photo

RMREJN62–. Colchicine in agriculture, medicine, biology, and chemistry. Colchicine; Colchicine. Experimental Growth in Animals 221 9.3 gives the results, with the percentages of dividing cells and of mitotic stages in control and colchicinized aninials.'^'^ From these results, it is apparent that mitotic arrest at metaphase has increased in six hours the number of cell divisions by 17.63/3.32. The mitotic duration, calculated as indicated in Section 9.2, is 3.32 X 6-0/17.63 = 1.13 = 1 hr. 8 min. It can be calculated from this result that in 37.7 hours (1.57 days), 100 per cent of the cells will have di

. Elements of biology, with special reference to their rôle in the lives of animals. Biology; Zoology. HEREDITY 311 200). Each cell now contains adjacent to the centrosome the 5 number of p and m chromosomes. The telophase is a period of nuclear reconstruction. The nuclear membrane appears and within it the chromosomes lose their distinctness, the chromatin becoming again a spireme, then scattering and remaining so until the prophase of the next mitosis. It has been found that in addition to the nuclear phenomena that characterize mitotic cell divisions, there are distinct changes in the physi Stock Photo

RMRCW4KR–. Elements of biology, with special reference to their rôle in the lives of animals. Biology; Zoology. HEREDITY 311 200). Each cell now contains adjacent to the centrosome the 5 number of p and m chromosomes. The telophase is a period of nuclear reconstruction. The nuclear membrane appears and within it the chromosomes lose their distinctness, the chromatin becoming again a spireme, then scattering and remaining so until the prophase of the next mitosis. It has been found that in addition to the nuclear phenomena that characterize mitotic cell divisions, there are distinct changes in the physi

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