FAUNISTIC NOTES AT PLYMOUTH DURING 1893—4. 211 
summer of the Tectibranch Philine aperta. Oscanius membranaceus 
also, though to a less extent, was unusually plentiful, penetrating 
even some distance up the Hamoaze. 
Another phenomenon which is probable referable to the same cause, 
although in a somewhat different manner, is the relatively greater 
abundance this year (1894) of many of the regular constituents of 
the bottom fauna. For example, the Hydroids Tubularia indivisa 
and a smaller form which appears to be Tubularia humilis, together 
with Coryne pusilla and Hudendrium ramosum, have been taken in 
the Sound this year in unusual quantity. The same remark applies 
to many Nudibranchs, and especially to the Molid Facelina coronata,* 
which has been remarkably common this year at Plymouth. I do 
not doubt that the unusual abundance of these and other forms may 
be directly attributed to the very favorable physical conditions under 
which the reproduction of their species took place in the preceding 
year. The destruction of larval life by physical agencies must then 
have been considerably Jess than the normal rate. Indeed, in the 
case of the oyster, as was attested by Prof. Herdman in a letter to 
Nature (July, 1893, p. 269), there was undoubtedly an unusually heavy 
fall of spat on the west coast of France last year, which implies that 
an unusually large percentage of larve were enabled to attach them- 
selves and to pass safely through the critical stages of their meta- 
morphosis ; and also, perhaps, that the reproductive activities them- 
selves were rather above the normal. 
So much for the general aspects of the fauna during the past 
eighteen months. Additional facts bearing out the above remarks 
may be gathered from the body of this paper. 
In the three succeeding sections are given—firstly, a list of the 
principal captures and additions to the fauna made since my lastt 
communication to this journal up to May 30th, 1894, when I left 
Plymouth ; secondly, some observations on the breeding seasons of 
marine animals at Plymouth; and thirdly, some remarks on the 
periodic changes in the constitution of the floating fauna. 
In several respects, however, I have to regret the incompleteness 
of my notes. They are compiled directly from my diaries, and are 
written on foreign soil, where I am without access to some of the 
appropriate works of reference and to several of my manuscripts. 
On this account the last two sections especially of this paper are 
offered simply as preliminary communications upon the interesting 
* I showed some years ago that the smaller Nudibranchs are annuals, and require only 
a year to attain their full growth. The same thing is true of Hydroids and many other 
Invertebrates (this Journal, 1890, p. 450). 
+ Notes on the Marine Invertebrate Fauna of Plymouth for 1892, vol. ii, 1892, pp. 333 
to 339. 
