HICK: VOLVOX IN YORKSHIRE. 169 
be due to differences in the amount of shelter afforded by the 
marginal vegetation on different sides of the pond, and to other 
influences which co-operate. 
Species.—Thanks to Klein’s admirable account of the specific 
distinctions of the forms of Volvox, a brief summary of which was 
given in my previous paper, it has been found easy to set up a few 
diagnostic characters by which the species collected may be readily 
determined, whether the colonies be sexual or asexual. The result 
is that of the two British species, V. aureus appears to be the 
commoner form in Yorkshire, as I have shown elsewhere to be the 
case in the district round Manchester. Of my old gatherings in 
Yorkshire I can only speak with certainty of that made at Rawcliffe 
in 1878, specimens of which I still have mounted as microscopic 
protoplasts. This, however, does not count for much, and it would 
be well to determine the forms at Askham and elsewhere—assuming 
they are still to be found—by direct observation. 
Of the three new localities brought to light last year, two 
undoubtedly yielded V. aureus, chiefly, if not entirely, viz., Midgely 
oor and Thornhill Lees. But experience has shown that too 
general a conclusion should not be drawn from a few gatherings, and 
that it is unsafe to transfer the character of the gathering to the pond 
whence it was obtained until experience has proved it to be constant. 
The case of Salterhebble may be cited in illustration of this. The 
first specimens sent me by Mr. Carnell I received in June, and 
were found to be the asexual colonies of V. g/obator. Subsequently, 
in July, specimens were collected by myself, and a much larger 
Supply obtained than could be sent through the post. These, on 
examination, proved to be V. aureus, and no example of V. globator 
Was noticed. At first I was inclined to think that a mistake had 
been made in the determination of the earlier sample, which, though 
Possible was scarcely probable, or that the two species were not 
really distinct, but capable of passing the one into the other. On 
comparison with the results obtained elsewhere, however, I came to 
the conclusion that the explanation is to be found in the fact that 
Sometimes both species co-exist in the same pond, but in widely 
different proportions, which are liable to vary under circumstances 
which cannot as yet be defined. In several instances, for example, 
I have had large gatherings of V. aureus in which isolated individuals 
June 1891. 
