268 EDWARD A. MINCHIN. 
was most convenient to me, as I was able at low tide to go 
down with a bottle of hardening reagents and preserve pieces 
of the sponge perfectly fresh from its native habitat, or in five 
minutes I could have fresh living pieces on the laboratory 
table. It was remarkable that I found no specimens of 
Leucosolenia botryoides in this pool, though it occurred 
in the very next pool to it, both species growing side by side. 
Before concluding it is my pleasant duty to express my 
best thanks to the committee of the British Association for 
appointing me to one of their tables in the Marine Biological 
Association Laboratory during three months of the summer 
of 1890, when I made the bulk of these observations ; to my 
friend Mr. Walter Garstang, then Assistant to the Director 
of the Marine Biological Association, for a great deal of help 
and advice; and, finally, to the delegates of the Common 
University Fund, Oxford, for appointing me to the Oxford 
table in the Naples Zoological Station, where I have been 
able to add a few observations to those made at Plymouth. 
ADDENDUM. 
Since the above was written two works have appeared by 
Dendy which I must notice. In his ‘ Organisation and Clas- 
sification of the Calearea Homocela, with Descriptions of the 
Victorian Species’ (‘‘ A Monograph of the Victorian Sponges,” 
part 1, ‘ Transactions of the Royal Society of Victoria,’ vol. iii, 
part 1, 1891), Dendy finds “ that the ectoderm of the Homo- 
cela agrees precisely with what Schulze has described for 
Sycandra raphanus, and what he himself found and 
described for Grantia labyrinthica. Except in very well- 
avoiding the light and seeking the darkest places as a well-marked character- 
istic of sponge larve. Now, in potholes like the two here mentioned, the 
larvee by avoiding the light would either settle under the overhanging edge, 
or down amongst the seaweeds. On the other hand, those that did not do so 
would inevitably be smashed by the waves. Hence it is probable, I think, 
that with more extended observations one could give a simple explanation of 
this habit, as well as a beautiful instance of the power of natural selection in 
producing it. 
