July 15, I9IS Rheosporangium A phanidermatus 287 



vacuole may persist till the degeneration of the supernumerary nuclei of 

 the egg has reached an advanced stage (PI. XLVII, fig. 2). Fertilization 

 may be delayed till the degeneration of the nuclei is nearly complete 

 (PI. XLVII, fig. 5); or in exceptional cases it may occur even before the 

 supernumerary nuclei have lost their nucleoli (PI. XLVII, fig. 6). It is 

 also apparent that the dense area at the center within which fusion occurs 

 may arise before the degeneration of the nuclei (PI. XLVII, fig. 6); or 

 it may not appear till after fertilization has occurred (PI. XLVII, fig. 2). 



This body, which at once suggests a coenocentrum, has been the 

 subject of much speculation. Its presence in the species to be described 

 is easily demonstrated. The functional nucleus of the egg takes a posi- 

 tion within it where it is joined by the male nucleus, and the two fuse 

 within it. Shortly after fusion it disappears, to be replaced by the 

 lypoid material and stored food of the oospore. Critical study of the 

 origin of the lypoid body, however, clearly demonstrates that the two 

 are entirely distinct. The suggestion that the coenocent rum-like body 

 is the early stage in the formation of a food vacuole is not tenable in 

 the case of this fungus, since that body is formed by the union of a 

 large number of small lypoid granules which first develop outside the 

 area in question, to coalesce later in the center of the spore (PI. XLVIII, 

 fig. 4, 6, 7, 10). On the other hand, it seems equally impossible to 

 regard it as a true coenocentrum originating from the centrosomes of 

 the degenerating nuclei. The fact that these nuclei degenerate without 

 pre\dous division raises a certain, although not unsurmountable, element 

 of doubt. The fact that it is not always present, even when degenera- 

 tion has reached an advanced stage (PI. XLVII, fig. 2), is significant, 

 but the most conclusive proof comes from the fact that it may appear 

 before degeneration has begun (PI. XLVII, fig. 6). In Plate XLVII, 

 figure 2, where the male nucleus has already entered the egg, the body 

 in question is not present, and the egg nucleus remains at one side. 

 It might be argued that the unusual position of the functional female 

 nucleus at this stage is to be explained by the absence of the body and 

 the consequent want of an attractive force to draw it to the center; 

 in other words, that the mass under discussion is, in fact, a coenocentrum. 

 It seems more logical to the writer, however, to reason that the same 

 force which causes the central vacuole to fill with denser protoplasm 

 continues to act and that the accumulation of the denser material of 

 the coenocentrum-like body, the return of the female nucleus, and the 

 approach of the male nucleus, as well as the subsequent accumulation 

 of food material in the center of the spore, are but manifestations of its 

 presence. 



It has already been noted that in fertilization a considerable quantity 

 of cytoplasm passes with the nucleus from the antheridium (PI. XLVII, 

 fig. 5). In preparations stained to show mitochondria it may be seen 

 that this cytoplasm carries a mass of mitochondria which are more 



