SOME PROBLEMS OF REPRODUCTION. 23 
plasm ; a small portion of granular protoplasm carries down a 
single male nucleus to fuse with the female one. The gono- 
plasm secretes an inner coat to the zygote, around which an 
outer one or “epispore”’ is secreted by the periplasm. The 
nuclei present in this layer can hardly be essential to the form- 
ation of the epispore, since no nuclei are present in the 
layer of epiplasm which does similar service to the endogenous 
spores of the Ascomycetes. We can only regard the nuclear 
divisions in “ oogonium” and antheridium as phylogenetic 
reminiscences of the formation of gametes by cell division ; 
the periplasm is thus equivalent to a number of degenerated 
gametes which have taken on the function of epispore form- 
ation; the multitude of gametes are sacrificed to the few. 
Obviously what we here term the “‘ oogonium” is neither 
morphologically nor physiologically the exact equivalent of a 
single oogonium in cellular, as distinguished from apocytial 
plants, but represents an apocytium of oogonial cells ; and the 
antheridium has a similar relation to the spermatogonium of 
cellular plants. 
The processes in those SaAPROLEGNIE#! that have been fully 
studied mark a distinct step further in the same path. The 
oangia are at first filled with multinucleated protoplasm ; 
vacuoles appearing and enlarging bring the nuclei closer 
together, and they soon fuse in pairs, a process continued 
until their number is materially reduced; while the mitoses 
observed in Peronospora do not take place. The primitive 
nuclei are vesicles with a central chromatin mass supported 
by a “linin” or nucleo-hyaloplasma network. In fusion of 
the nuclei the chromatin masses long remain distinct, but 
are smaller and take up stain less readily, and the nuclear 
wall at this stage ceases to stain, so that the fusion nuclei 
have the look of vacuoles in the cytoplasm containing a 
variable number of chromatic granules. During this stage 
the true vacuoles unite to form a large central cavity into 
which fresh vacuoles open, so that the protoplasm forms a thick 
1 The following account is largely taken from an original paper of my own 
“On the Cytology of Saprolegniex,” still incomplete and unpublished. 
