104 FECUNDATION J HETEROGAMETES. 



kinetically, thereby doubling their number, which may be ten times 

 greater than the number of egg-cells produced in the oogonium. 

 According to Trow the nuclei reveal a structure similar to that in the 

 higher plants. Immediately following the division of the nuclei rapid 

 changes take place, whose interpretation has led to differences of 

 opinion. In both Saprolegnia and Achlya, according to Trow, only 

 as many nuclei remain functional in the oogonium as there are egg- 

 cells developed, the supernumerary nuclei being digested immediately 

 after the karyokinesis mentioned above (Fig. 38, B). In Achlya 

 americana the appearance of the supernumerary nuclei suggests that 

 they may possibly divide again before disorganization. In Saprolegnia 

 the same author states that some of the degenerating nuclei do really 

 appear to unite in pairs. Hartog, on the contrary, maintains that the 

 diminished number of nuclei was brought about by nuclear fusions, 

 and consequently each functional nucleus remaining in the oogonium 

 is the result of such fusions. Judging from what we now know of 

 the behavior of nuclei in multinucleated sexual organs in which the 

 sexual nuclei are not the product of nuclear fusions, and from the 

 evidence which Trow has furnished, I am inclined to believe that the 

 evidence is in favor of his conclusions, namely, that the functional 

 nuclei of the egg-cells are not the result of fusions. 



As is well known the cytoplasm now begins to ball up in masses 

 which eventually form the egg-cells (Fig. 37, B, C). In each mass, 

 as in the completely differentiated egg, only one functional nucleus is 

 present. Accompanying or surrounding this nucleus is a conspicuous 

 mass of finely granular cytoplasm, which, although appearing less 

 highly differentiated than in certain Peronosporece, may have a similar 

 function. The young egg rapidly becomes spherical and is provided 

 at first with a plasma membrane only. The details in the cytoplasmic 

 differentiation of the egg-cells have not, as yet, been critically worked 

 out, except in so far as that is possible in the living specimen or from 

 observations of the organs in toto. Whether the balling of the proto- 

 plasm described by both earlier and more recent observers is a cleavage 

 such as is known to take place in other Phycomycetes can not be 

 affirmed positively, but the facts seem to indicate a similar cleavage 

 or a closely related process (Fig. 37, B, C). 1 



The antheridia, as is also well known, are developed from the ends 

 of filaments which apply themselves closely to the surface of the oogo- 

 nium (Fig. 37, D). When the cross-wall is formed, separating the 



1 The process of the differentiation of the egg-cells as described in the foregoing paragraph is con- 

 firmed by the very careful observations of B. M. Davis on Siprolegnia, mixta The manuscript of 

 these pages had left my hands before the receipt of Professor Davis's paper. 



