432 THE OPISTHOBRANCHIATE 



semblance of their cerata in brightness and similarity of colour 

 and external form to the upper ends of the zooids of Clava. 



It is an interesting fact that at Plymouth this species has never 

 been found upon gymnoblastic Hydroids, but always upon Calypto- 

 blasts, chiefly Plumularia, AntennuLaria, and Sertularia^ (especially 

 8. 'pumila). Clava cornuta and mvlticornis are to be found covering 

 the under sides of stones and the bottoms of certain rock-pools on 

 the shore, but I have searched these colonies in vain for a single 

 specimen. Correlated with this dissimilarity of habit, Plymouth 

 specimens very rarely show much of the bright rose-colour generally 

 found in the species elsewhere. One such individual, however, was 

 found creeping over a brightly coloured scallop-shell {Pecten magcimus) 

 upon which colonies of Halecium were growing. The Halecium had 

 large quantities of the spawn of D. coronata attached round the 

 bases of its stems, some of which no doubt had been deposited by 

 this individual. If so, the Doto either was wise in keeping near 

 the brightly coloured shell to deposit its eggs, or had been creeping 

 over the Hydroid, in spite of its conspicuous coloration, with 

 impunity. 



Family— MOhYDlBM. 



Suh-family 1. — ^olidin^ ( = ^OLiDiADiE peopri^, Bergh). 

 17. yEoLis, Cuvier {sens, strict.). 

 21. ■^^oLis PAPiLLOSA, Linn. 



Three specimens only have been taken this year, under stones at 

 low water ; one in April at Drake's Island, another in May immedi- 

 ately below the Laboratory, and the third was found by Dr. Fowler 

 on July 16th at the east end of Drake's Island. Mr. Vallentin 

 found it abundant in the spring in Falmouth Harbour, on the under 

 side of rocks at low water. 



In my former Report^ I had occasion to refer to the resemblance 

 of this species in colour and form to the Actinian Sagartia troglodytes, 

 noticed and recorded by M. Giard, who also observed that the two 

 creatures were frequently to be found in the same situations. As 

 this is one of the most important of the 'Hests of mimicry '' given 

 by Wallace, I was inclined to regard j^olis papillosa as an instance 



1 Cf. Mcintosh, Mar. Inv. and Fishes, St. Andrews, 1875, p. 86. Mr. Vallentin finds 

 the species common at Falmouth on Obelia geniculata. I have found it on this Hydroid 

 occasionally at Plymouth. 



^ L. c, pp. 175, 191. Sagartia parasitica on the former page was obviously an error, and 

 I take this opportunity of correcting it. 



