547 
Trow. — On Fertilization in the Saprolegnieae . 
based on the fact that he attaches extreme importance to the occasional 
occurrence of binucleate and trinucleate oospores in the apandrous species 
examined by him, a phenomenon which appears from its infrequency and 
the author’s drawings and methods of culture to be in all probability of 
a pathological character. It is simply unfortunate that Davis should have 
ventured to enter upon such a controversy upon the basis of the examination 
of an obviously apogamous form ; especially as it is clear that his methods 
would, if diligently followed out on appropriate material, have inevitably 
led him to the perception of the truth as to fertilization. There can, 
indeed, be no doubt at all that if he had examined a typical species — one 
i. e. with antheridia — he would have observed the succession in the number 
of the nuclei which has been already described, and have been compelled to 
modify his views accordingly. While his material was admirably suited to 
enable him to study the development of the oospheres and oospores, 
untrammelled by the difficulties associated with the presence of antheridia 
and fertilization-tubes, it is almost inconceivable that any one should choose 
it to enable him to take part in the settlement of those controversial 
questions which have been raised by the recent study of species of Achlya 
and Saprolegnia. Such an apogamous form as was examined by Davis is 
exceptional in the genus Saprolegnia. I have not yet succeeded in my 
endeavours to collect one in the genus Achlya. In cytology, as elsewhere, 
it is best and safest to proceed from the rule to the exception and not from 
the exception to the rule. These observations of Davis, however, impelled 
me to seek for another species of Saprolegnieae in the hope of verifying his 
observations on the so-called ‘ coenocentrum.’ 
With the assistance of Mr. Pole-Evans, Achlya De Baryana, Humphrey, 
was obtained, and proved in every way a most desirable subject for 
experiment and observation. The communications to be made on these 
two species of Achlya will, it is to be hoped, dispose finally of the vexed 
question as to the occurrence of fertilization in the Saprolegnieae. 
Methods. 
It is very desirable that the work already done on the Saprolegnieae 
should be extended and amplified as well as confirmed. A short account of 
the methods used by me, the result of the experience of the last ten years, 
may be of service to those who wish to specialize in this promising field of 
research. It has been pointed out in earlier papers that the Saprolegnieae 
may be easily collected and cultivated. Fine cultures of single well- 
identified species are highly desirable for cytological work, and they are 
readily obtainable if attention be paid to a few simple particulars. Excellent 
nutrient material for the cultures is provided by house-flies, which should be 
killed by chloroform, placed in plugged test-tubes and thoroughly sterilized. 
These flies will, if properly prepared, keep in good condition for several 
