NUDIBRANCHIATA OF THE L.M.B.C. DISTRICT. 101 
Island, on 26th June, 1887, and on both the North and 
South Spits in May, 1889. 
Dendronotus arborescens, Muller. 
The variations in the abundance of this species at 
Hilbre Island were commented upon in the last report. 
In September, 1888, it was so abundant that forty to fifty 
specimens were collected in about fifteen minutes, while 
at the next visit to Hilbre, in the beginning of March, 
1889, only a few specimens were seen, and in April none 
were found. 
As Professor Herdman has recorded in the ‘“‘ Second 
Annual Report upon the Puffin Island Biological Station,’’* 
a number of specimens collected at Hilbre Island were 
carefully taken to Puffin Island, last September, and 
placed in suitable spots on the South Spit. They dis- 
appeared and have not since been seen, but would hardly 
be expected to appear again on the shore till later in the 
summer. 
As this species is of large size, and is relatively abun- 
dant in this neighbourhood, we have made use of it for 
anatomical purposes, and shall now place on record some 
observations we have made as the result of our sections 
and dissections of a considerable number of specimens. 
Alder and Hancock, in their Ray Society Monograph, + 
gave a general account of the anatomy of Dendronotus, 
illustrated by drawings of dissections of various parts. 
Recently Dr. Rudolph Bergh, in his Report upon the 
Nudibranchiata collected during the ‘‘ Willem Barents”’ 
expedition, { gave some further details in regard to the 
= ‘Proc. Biol. Soc., L’pool, vol. ii1., p. 29. 
+ Loc. cit. Part ii., fam. 3, pl. ii. 
£ ‘Bijdragen tot de Dierkunde.” Natura artis magistra, Afl. xiii., viii. 
p. 25, Amsterdam, 1886, 
