﻿1903] OOGENESIS IN SAPROLEGNIA 247 



potential gamete nuclei, but, so far as we know, only one of 

 these becomes functional. But it would not be surprising to 

 find at any time binucleate or trinucleate eggs among species of 

 Albugo that are normally uninucleate. 



In concluding, we must lay emphasis upon the importance of 

 the coenocentrum as an index of the activities peculiar to 

 oogenesis in Albugo, Peronospora, Sclerospora, Pythium, and 

 Saprolegnia. Although this structure is probably in large part 

 the expression of activities of the protoplasm as a whole, still 

 there can be no doubt of its material existence. It is difificult 

 to understand how Trow (1901, p. 291) can question this point, 

 except that his figures indicate that fine details of structure were 

 not shown in his preparations. 



It would be strange, indeed, if so large a mass of protoplasm 



as the coenocentrum should not react in turn on the protoplasm 



that gave it birth. The coenocentrum is not a mass of food 



material, even though much of its granular substance may be 



the products of metabolism, and the structure as a whole tropho- 



plasmic in character. It is protoplasm, and as such must be 



counted a factor in the subtle processes of oogenesis. Trow's 



comparison of the coenocentrum to a whirlpool in a river is not 



good, for there is unquestionably in this structure the expression 



of chemical phenomena as well as physical. The evidence is 



very strong from Stevens's (1901) work on Albugo, and the 



present study on Saprolegnia, that the coenocentrum has a 



sphere of chemotactic influence on the nuclei in its neighbor- 

 hood. 



SPOROGENESIS, 



Except for a recent paper by Timberlake (1902) on Hydro- 

 dictyon, we know little of the details of zoospore formation in 

 either algae or fungi, and the field would certainly repay inves- 

 tigation. The writer examined the sporangium of Saprolegnia 

 ^txta to contrast the conditions there with the processes of 

 oogenesis, but, the subject not being favorable, little came of 

 the study, except a general confirmation of the accounts of 

 sporogenesis given by Rothert (1888), Hartog (1888), and Hum- 

 phrey (1892). If the oogonium is the homologue of the sporan- 



