232 Prof. W. C. M‘Intosh on the 
untplicatum on Leptogorgia. Hermwa, a transparent Nudi- 
branch on a reddish weed (Grifithsta), has a reddish outline 
and a greenish aspect on green seaweed, ‘This coloration is 
probably due to the contents of the intestine. Some mollusks, 
like the limpet, chiton, periwinkles, and certain Nudibranehs, 
are more or less in harmony with their surroundings; and 
the same may be said of Trochus ltneatus on the granite rocks 
of Cobo Bay, Guernsey. A red Doris, probably D. concinna, 
frequents Hymeniacidon sanguinea, and Xenophora attaches 
fragments of shell, rock, and coral to the edges of the growing 
shell, and thus resembles its surroundings. ‘The common and 
Johnston’s sea-lemons (Archidoris tuberculata and A. John- 
stont) may, as insisted on by Prof. Herdman and Mr. Garstang, 
be protectively coloured so long as they remain contracted 
and quiescent. Yet it must be noted that the colours of 
A. tuberculata vary, some being gaily tinted with yellow and 
purple, others, especially under large stones in tidal pools, 
having more sober hues. Moreover, the species is found not 
only on the surfaces of Halichondria, on which it feeds, but 
under ledges amongst the red Styela grossularia and zoophytes, 
under large stones, and occasionally on the surface of rocks 
and Fuct at low water. It must also be borne in mind that 
A, Johnston accompanies it in its haunts, especially on Halt- 
chondria, the hues of which it much more closely resembles 
than A. tuberculata. It may well be asked why the latter has 
not more closely adapted itself to the colour of the sponges on 
which it feeds. 
Again, the smaller examples of Doris repanda are “of a 
pure waxy semitransparent white”? (Alder and Hancock), and 
the largest are dusky yellowish, colours which are conspicuous 
in a rock-pool, especially as they sometimes crawl on the 
blades of fuct fringing the margin. The border of the mantle 
in many is injured, as if a portion had beenremoved. Doris 
aspera, which occurs under stones near low-water mark, is 
equally prominent, most being white, though a few are 
yellow. The tints of the abundant Doris bilamellata likewise 
do not seem to be protective between tide-marks, where they 
are met with all the year round, as is the case also with the 
conspicuously whitish Goniodoris nodosa, usually found under 
stones in tidal pools. These and the brilliantly coloured Triopa 
claviger are at once detected when the stone is upturned ; 
but they are not wholly confined to such localities, and all are 
occasionally tossed on shore by storms on the blades or roots 
of tangles. If some would hold that the conspicuous whitish 
coloration is thus shielded by their habit of living under stones, 
what is to be said of their associate Zgirus punctilucens, which 
ce 
