Trow . — The Karyology of Saprolegnia. 615 
siderable interest, but furnish no real evidence of the existence 
of fusion-nuclei. The figure of a binucleate oospore of Achlya 
americana , together with Hartog’s statements concerning 
another species of Achlya , are the grounds for my belief that 
fertilization takes place in Achlya as well as in Saprolegnia. 
My own studies have led me to conclusions which differ 
fundamentally from those advanced by these three observers. 
The results brought forward in the present paper will, 1 trust, 
help us to form definite conclusions respecting these dive^ent 
and strikingly contradictory views. 
In his investigations, Humphrey adopted the method of 
imbedding in paraffin and cutting serial sections with the 
microtome. His material was stained en masse by haema- 
toxylin and then imbedded and sectioned. I have tried this 
method, but have not been able to obtain good results with 
it. Hartog and Dangeard have apparently trusted to prepara- 
tions involving fixing, staining, clearing and mounting only. 
Such methods may suffice to elucidate the structure of the 
zoospores and mycelium together with their nuclei, but it 
appears to me to be totally inadequate to solve the difficult 
problems presented by a study of the sexual organs. Hartog’s 
observations, nevertheless, so far as they go, appear to be most 
accurate and reliable, and it is only in the interpretation of 
them that I differ widely from him. 
The question of the formation and liberation of the 
zoospores, which since 1880 has attracted the attention of 
a very large number of botanists, cannot be entered into here. 
The figures of sections of sporangia here given are intended 
only to illustrate the behaviour of the nuclei. 
Methods. 
As the genus Saprolegnia is admirably adapted for teaching 
purposes and has been strangely neglected by the writers of 
text-books, it may serve more than one useful purpose if 
a somewhat extended account be given of the methods adopted 
in this research. 
