Archive image from page 41 of The development of the human. The development of the human body : a manual of human embryology . developmentofhum00mcmu Year: 1914 30 THE MATURATION OF THE OVUM (Fig. 15, oc1) and at the metaphase a dyad from each tetrad passes into each of the two cells that are formed. These two cells (second- ary oocytes) are not, however, of the same size; one of them is almost as large as the original primary oocyte and continues to be called an ovum (oc2), while the other is very small and is termed a polar globule (ft). A second division of the ovum quickly succeeds the fi
Archive image from page 41 of The development of the human. The development of the human body : a manual of human embryology . developmentofhum00mcmu Year: 1914 30 THE MATURATION OF THE OVUM (Fig. 15, oc1) and at the metaphase a dyad from each tetrad passes into each of the two cells that are formed. These two cells (second- ary oocytes) are not, however, of the same size; one of them is almost as large as the original primary oocyte and continues to be called an ovum (oc2), while the other is very small and is termed a polar globule (ft). A second division of the ovum quickly succeeds the first (Fig. 15, oc2), and each dyad gives a single chromosome to each of the two cells which result, so that each of these cells possesses half the number of chromosomes characteristic for the species. The second division, like the first, is unequal, one of the cells being relatively very large and constituting the mature ovum, while the other is small and is the second polar globule. Frequently the first polar globule divides during the formation of the second one, a reduction of its dyads to single chromosomes taking place, so that as the final result of the maturation four cells are formed (Fig. 15), the mature ovum (o),and three polar globules (ft), each of which contains half the number of chromosomes characteristic for the species. The similarity of the maturation phenomena to those of sper- matogenesis may be perceived trom the following diagram: n/'~N Spermato- ( J cyte I Spermato- cyte II Ovum Oocyte II O O OO
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