Trow . — On Fertilization in the Saprolegnieae. 565 
the earlier ones, as almost invariably occurs in all genuine investigations. 
The results in these four species are as follows : 
1. Achlya polyandra has the formula I, 2, 1, established in 1902. 
2. .Achlya americana cambrica „ 1, 2, 1, ,, ,, 1897. 
3. Saprolegnia dioica „ I, 2, 1 ? „ „ 1895. 
4. Saprolegnia mixta „ 1, 1 or 2, 1 ,, „ 1895. 
Wager (’ 99 ) has confirmed the fundamental points of my earlier work. 
His formula would be 1, 2, x. He appears strongly inclined to the view 
that fertilization must take place, but expresses himself with commend- 
able caution. 
The negations of Har tog and Davis . Hartog apparently still adheres to 
his original view as to the wholesale fusion of nuclei in the oogonium, but 
since Davis has confirmed my results as to this point, and the above 
detailed observations show that no such fusions could possibly take place 
in these forms, there seems no adequate reason for subjecting his very 
pointed criticisms of my work to a detailed examination. The policy 
of appealing to fact, and of avoiding a war of words, finds ample justi- 
fication. 
Davis, however, is inclined to adopt Hartog’s view — supported as it 
was a few years ago by the almost universal belief in the complete apogamy 
of the Saprolegnieae — that normal fertilization does not take place in this 
group. His contentions seem to me to be refuted by the facts described 
above, so that the necessity for a detailed examination of his criticisms 
likewise no longer exists. Moreover, the investigation of Achlya De 
Baryana having led to the discovery of the second mitosis, and of the 
centrosome and astrosphere associated with the sperm-nucleus in fertiliza- 
tion, it becomes necessary that Davis’s species should be reinvestigated so 
as to test his view of the origin of the ‘ coenocentrum.’ The question of 
the occurrence of a second mitosis in apandrous oogonia, and of the fate 
of the nuclei in these organs, forms a very difficult but interesting problem 
for future investigation — one, indeed, that should prove profitable in the 
highest degree. 
Conclusion. 
The problem of fertilization in the Saprolegnieae is, it seems to me, to 
a certain extent solved. Some species are typically sexual, others obviously 
apogamous. Between these extremes there are intermediate types. It is 
to be hoped that some of those able cytologists who have already done 
such good work on the Peronosporeae will turn their attention to the 
Saprolegnieae. Those who take up the study of such forms as Achlya De 
Baryana and Achlya polyandra will soon find themselves in a position to 
