THE ORGANIC CELL 
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dyads equal to one half the usual number of chromosomes. 
The egg at once forms the second polar body, without any 
intervening reconstruction of the nucleus. Each dyad splits to 
form two single chromosomes, two single ones remaining in the 
egg, the other two going to the second polar body. According 
to this arrangement, both egg and second polar body each 
receive two single chromosomes, which is one half of the original 
number. The two remaining in the egg now form a nucleus. 
The Genesis of the Spermatozoon. 
The number of 
* divisions is greater 
Growth 'period 
„ Maturation period 
(Boveri.) 
Reduction in the Male. 
Reduction in the male is a similar process to that main- 
taining in the female. In the same way as the ova the sper- 
matozoa are descended from the primordial germ cells, which, 
undergoing mitosis, produce the spermatogonia. In the same 
manner as the oogonia, the spermatogonia continue to divide 
for a time, possessing the full number of chromosomes, i.e. 
four in Ascaris . The process of division is arrested for a time, 
and the spermatogonia enlarge to form spermatocytes. Each 
spermatocyte divides twice in rapid succession, the first division 
producing two daughter spermatocytes, the second division 
four spermatids, each of which becomes a spermatozoon. The 
chromatin reduction occurs in an exactly similar manner as 
in the case of the ovum, each spermatozoon receiving one half 
the usual number of single chromosomes. 
