378 Dr. Reid on the Development of the 
borders to the object upon which it was deposited. The process 
of spawning did not seem to occupy any very great length of 
time. ‘The other pair was seen im coitu nine days after I had 
taken them home, and when examined thirteen hours after this 
neither had spawned, but two howrs later one had spawned and the 
other was spawning. The animals by spawning became consider- 
ably reduced in size. They were kept alive for three weeks, and 
they deposited small portions of spawn between ten and fourteen 
days after the first spawning. It does not however appear to be 
absolutely necessary for the production of fertile ova im all, if in 
any of the individuals of the Nudibranchiate Mollusca, that a 
coitus should have so shortly preceded spawning as was observed 
in the Polycera, for an Eolis which was kept strictly confined in 
a vessel by itself, deposited, on the tenth and again on the thirty- 
second day of its isolation, abundance of fertile ova. During the 
high spring tides at the end of last February, I found near low- 
water mark several large assemblages of Goniodoris Barvicensis 
and Doris bilamellata among the rocks, collected for the purpose 
of breeding*. In one of these groups there must have been at 
least between sixty and seventy individuals of the G. Barvicensis, 
and abundance of their spawn adhered to the surface of the rocks, 
and in one place a portion about six inches square was almost 
completely covered by it. Many of the Doris bilamellata had 
also spawned, and were collected in smaller, more numerous and 
scattered groups, the greater number of which were farther from 
low-water mark and in more exposed situations than those of 
the G. Barvicensis. These assemblages do not break up for some 
time, but continue to occupy nearly the same position, and the 
animals composing them spawn more than once. I found some 
individuals still limgering among the rocks, and recent spawn de- 
posited, as late as the end of April. Several pairs of the Doris 
tuberculata were also observed, and I procured four specimens 
of Dendronotus arborescens and two specimens of the Holis men- 
tioned above. The individuals of the two last genera mentioned 
were not found in pairs, and these, along with several specimens 
of Goniodoris Barvicensis and Doris bilamellata, were taken home 
and kept until they had spawned. About the same time I pro- 
cured several specimens of Doto coronata from the deep sea ad- 
hering to Plumularia faleata and Thuiaria thuia, which were also 
kept alive, and began to spawn about the middle of March. Near 
the end of March I found a considerable quantity of the spawn 
of the Doris tuberculata adhering to the under surface of the 
ledges of rock near low-water mark. 
The spawn of the Doris bilamellata, D. tuberculata, Doto coro- 
* From the unusual mildness of this spring, the breeding-season may have 
commenced earlier than usual. 
