﻿1903] OOGENESIS IN SAPROLEGNIA 343 



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There is one mitosis in the oogonium, the spindle being 

 intranuclear. There are no centrosomes. The four chromo- 

 somes are derived from the linin network. 



The daughter nuclei following the mitosis are much smaller 

 than their parents. They shortly give evidence of coming 

 degeneration, the nuclear membranes become indistinct, and the 

 contents finally lie as granular material in clear areas resembling 

 vacuoles. 



The eggs are formed during the process of nuclear degenera- 

 tion. The protoplasm in the oogonium at this period is arranged 

 peripherally around a large central vacuole. The ooplasm col- 

 lects around several centers, each of which is to become an e 

 origin. The egg origins are finally separated through the 

 arrangement of vacuoles which results in the severance of con- 

 necting strands of protoplasm, and the eggs round themselves 

 off as independent structures. 



The differentiation of the egg origins takes place around a 

 deeply stained protoplasmic body, the coenocentrum, from 

 which delicate fibrillae radiate. The coenocentra are formed 

 de novo, one for each spore origin. Each is at first a small 

 globule, made conspicuous, however, by its fibrillar rays. It is 

 most conspicuous in the young eggs, becoming less distinct with 

 the ripening, and finally disappears. There is no trace of it in 

 the oldest eggs. 



The coenocentrum is a protoplasmic structure, but not a 

 permanent organ of the cell. It is probably the morphological 

 expression of Aynzmxc activities in the oogonium when the egg 

 origins are differentiated, and is a sort of focal point of the 

 metabolic processes peculiar to oogenesis. 



The coenocentrum exerts a chemotactic influence on any 

 nuclei in its immediate vicinity. Generally one nucleus is 

 selected and comes to lie very close to the coenocentrum, so 

 that these two structures in the egg origins may be separated 

 only under high magnification. This nucleus increases In size 

 when all other nuclei in the egg origins and young eggs are 

 degenerating, showing that it is greatly favored with respect to 

 nourishment by its position near the coenocentrum. 



