23!) PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
General Considerations. 
Stevens (:Olb) has reached the conclusion that a well organized 
coenocentrum, a uninucleate egg, and a small receptive papilla are 
marks of higher and more recent forms of the genus Albugo. For 
example, he finds only a rudimentary coenocentrum in the multi- 
nucleate egg of Albugo portulacae which he regards as the most 
primitive, and a highly developed structure in the center of the 
uninucleate oosphere of A. Candida , the most highly developed 
member of the genus. He furthermore finds that Albugo tragopo- 
gonis represents a transitional stage between the two previously 
mentioned species. At the outset its oospheres contain many nuclei 
only one of which is finally sexually functional ; the others may be 
found in all stages of degeneration. He therefore concludes by the 
law of biogenesis that A. portulacae is the most primitive and that 
the condition obtaining in A. Candida has been brought about by a 
process of evolution. 
The writer believes that the ontogeny of Araiospora confirms 
Stevens’s theory that the uninucleate condition has been evolved from 
previously existing multinucleate forms. The formation in the cyto¬ 
plasm of the developing oogonium of many small, often barely con¬ 
spicuous, fine meshed masses which, as the oogonium develops, 
finally fuse at its center and function there as an attraction for the 
sexual nuclei, if given a phylogenetic interpretation, certainly sug¬ 
gests relationships with earlier forms which had either multinucleate 
oospheres or multiovulate oogonia. In either case, and particularly 
in the latter, we may see evidences of more primitive forms in the 
Saprolegniaceae. In this connection, Davis’s (: 03 ) investigations are 
of interest. He finds several star-like coenocentra forming in the 
developing oogonium; one coenocentrum and the nucleus which 
always accompanies it, form the center of each developing egg. 
These observations seem to give confirmation to the theory that 
uninucleate forms are the more recent. 
Wager and Stevens are not in agreement as to the homology of 
the receptive papilla of the Peronosporineae. Wager believes it to 
be strictly homologous with the receptive spot in the oospheres of 
Oedogonium and* Vaucheria. Stevens, on the contrary, sees no 
homology between this structure and the receptive papilla of the 
