MARIN3 BIOLOGICAL STATION AT PORT ERIN. 121 



sea-lemon (Archidoris tuberculata) frequently found in 

 rock pools during the spring and summer ; 2 is the rarer 

 and smaller Polycera quadrilineata, marked with yellow 

 spots and found sometimes creeping on the blades of 

 Laminaria; 3 is Eolis tricolor, one of the most graceful 

 and brilliantly coloured of the sea-slugs ; and 4 is the 

 little Doto coronata found on colonies of Zoophytes, upon 

 which it feeds. The brightly-coloured projections on the 

 back of Eolis have batteries of microscopic stinging 

 threads which can be discharged instantaneously into any 

 offending animal. Those sea-slugs which have no stinging 

 organs are for the most part coloured and shaped so as 

 to closely resemble their natural surroundings, and so 

 escape the observation of their enemies, while those (like 

 Eolis) with offensive organs are conspicuous and bril- 

 liantly coloured, as if to warn other animals to avoid 

 them. In losing the shell these Molluscs have lost a 

 protection against injury, and this loss is compensated by 

 the colours and appearance of the soft bodies, which in 

 some cases are of a protecting and in other cases of a 

 warning nature. The spawn of the sea-slugs is deposited 

 in long ribbon-like or cord-like convoluted white masses 

 on stones and weeds. A small piece contains many 

 hundreds of minute embryos which, when hatched, have 

 for a time little cap-like shells. This leads us to believe 

 that the sea-slugs are descended from ordinary shell- 

 bearing Molluscs. 



Papers and reports upon the Nudibranchs, by 

 Professor Herdman and Mr. Clubb, will be found in our 

 volumes. 



