Calma Glaucoides : A study in adaptation. 



By 

 T. J. Evans, M.A. (Oxoii.), 



Lecturer in the Medical School, Guy's Hospital, London University. 



With Plate 11 and 3 Text-figures. 



A DETAILED description of certain portions of the anatomy 

 of a small British mollusc is here submitted, not so much as 

 an extension of our knowledge of molluscan structure, as on 

 account of the general biological interest of a unique metabolic 

 type. 



Whilst retaining the shape and general structural plan of an 

 aeolidiomorph Nudibranch, Calma presents a combination of 

 important departures from that type which may all be directly 

 or indirectly referred to its specialized diet, namely, the eggs 

 and embryos of the smaller shore fishes. So close is the external 

 resemblance to the Aeolid that Alder and Hancock originally 

 (1, PI. xxii, letterpress) placed it in Cuvier's genus Eolis, 

 whereas the modifications to be described are in some respects 

 so great as to be comparable with those associated with 

 a parasitic life. 



The genus has been recorded only from European waters, 

 and contains Calma glaucoides of Alder and Hancock, 

 commonly taken at Plymouth, Eoscofi", and Concarneau, the 

 Eolis albicans of Friele and Hansen (6) from the North 

 Atlantic, and the Forestia mirabilis of Trinchese (9) 

 from the Mediterranean. All three will probably be found on 

 re-examination to belong to one species, C. glaucoides. 



At Eoscoff, Hecht (6) found the animal feeding during June 

 and July on developing eggs of Cottus, Lepadogaster and 

 Liparis under stones, and iu September in the swollen radical 



