232 Prof. W. C. M'Intos!. on the 



uniplicatum on Leptogorgia. fTermaa, a transparent Nudi- 

 branch on a reddish weed {Grijfithsia), has a redilish outline 

 and a greenish aspect on greei\ seaweed. This coloration is 

 probably due to the contents of the intestine. Some mollusks, 

 like the limpet, chiton, periwinkles, and certain Nudibranchs, 

 are more or less in harmony with their surroundings; and 

 the same may be said of Trochus lineatus on tlie granite rocks 

 of Cobo Bay, Guernsey. A red Don's, probably D. concinna, 

 frequents IJyineniacidon sanguinea, and Xenophom attaches 

 fragments of shell, rock, and coral to the edges of the growing 

 shell, iind thus resembles its surroundings. The conmion and 

 Johnston's sea-lemons {Archidoris tuhercuJata and A. John- 

 stoni) 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. I\roreover, the species is found not 

 only on the surfaces of Halickondria, 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 Fuci at low water. It must also be borne in mind that 

 A. Johnstoni accompanies it in its haunts, especially on llali- 

 chondrue, 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 Fuci fringing the margin. The border of the mantle 

 in many is injured, as if a portion had been removed. 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 hilamellata 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 Ooniodoris 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 cons])icuous whitish 

 coloration is thus shielded by their habit of living under stones, 

 what is to be said of their associate /Egirus punctilucensy which 



