. Principles of modern biology. Biology. 478 - Heredity and Evolution o / \ / \ / \ ooo»oooo /\ A A A A A A A 0000000*00000000 ZYGOTE EMBRYONIC DEVELOPMENT 9 O • / \ \ o o o • O A o o A A /\ / \ / \ • • • • A A /\ A •••••••• PRIMORDIAL GERM CELLS OOOOOOOfOOOOOOOO A A • • • • A A A A / \ TESTIS 1 SPERMATOCYTE t / SPERMATIDS • • SPERM GONIA A A • • • • A A A A OVARY AUXOCYTES GROWTH PERIOD MATURATION DIVISIONS (MEIOSIS) 1 OOCYTE. A POLAR BODIES EGG ZYGOTE Fig. 26-3. History of the germ cells in multicellular animals; germ cells black, somatic cells white. The number of cell divisions is actually
. Principles of modern biology. Biology. 478 - Heredity and Evolution o / \ / \ / \ ooo»oooo /\ A A A A A A A 0000000*00000000 ZYGOTE EMBRYONIC DEVELOPMENT 9 O • / \ \ o o o • O A o o A A /\ / \ / \ • • • • A A /\ A •••••••• PRIMORDIAL GERM CELLS OOOOOOOfOOOOOOOO A A • • • • A A A A / \ TESTIS 1 SPERMATOCYTE t / SPERMATIDS • • SPERM GONIA A A • • • • A A A A OVARY AUXOCYTES GROWTH PERIOD MATURATION DIVISIONS (MEIOSIS) 1 OOCYTE. A POLAR BODIES EGG ZYGOTE Fig. 26-3. History of the germ cells in multicellular animals; germ cells black, somatic cells white. The number of cell divisions is actually much greater than shown here (except in the maturation period). (Adapted from Wilson.) pronounced; and due to an accumulation of plasm among the four resulting daughter yolk, the primary oocyte becomes very much cells (Fig. 26-3). One cell, which is the ripe larger than the primary spermatocyte. But egg, receives virtually all the accumulation more important still is the fact that the two of yolk and cytoplasm, whereas the polar meiotic divisions that follow are highly bodies receive only an insignificant fraction unequal as to the apportionment of cyto- (Fig- 26-5). Thus the ripe egg, if fertilized, is. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marsland, Douglas, 1899-. New York, Holt, Rinehart and Winston
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