1.78 



ORGANS OF TOUCH 



forms {Glandina, Aerope, compare Fig. 21, p. 54) these palpae are of 

 great size, and curl upwards like an enormous pair of moustaches. 



Fig. 9)\. — Cijpraea moneta L., showing tentaculae at 

 edge of mantle, which partly envelopes the shell : 

 Si, siphon ; M, M, mantle ; F, foot ; T', tenta- 

 culae at edge of mantle. (After Quoy and Gai- 

 mard). x f. 



Fia. 82. — Monodonta canali- 

 fera Lara., New Ireland, 

 showing mantle lobes. 

 (After Quoy and Gai- 

 mard.) 



Fig. 83. 

 seizin 



■ Glandina 



When a Glandina seizes its prey, the palpae (see Fig. 83) appear 

 to enfold it and draw it in towards the mouth. 



It is in the Opisthobranchiata that the organs of touch 

 attain their maximum development. Many of this group are 

 shell-less or possess a small internal shell, and accordingly, in the 

 absence of this special form of defence, a multiplied sense of 

 touch is probably of great service. Thus we 

 find, besides the ordinary cephalic tentacles, 

 clusters or crowns of the same above the head 

 of many Nudiljranchiata, with lobe-like pro- 

 longations of the integument, and tentacular 

 processes in the neighbom^hood of, or surround- 

 its prey, i^^g the branchiae (see Figs. 58 and 84), or even 

 with buccal papii- projecting from the whole upper surface of the 



lae turned back. i- /-in 



(Strebei.) body (Fig. 5, C). 



In the Pelecypoda, the chief organs of touch 



are the foot,wdiich is always remarkably sensitive, especially towards 



its point, the labial palps on each side of the mouth, and the 



siphons. In certain cases the mantle border is prolonged into a 



series of threads or filaments. These are particularly noticeable 



in Pecten, Le'pton, and Lima (Fig. 85), the mantle lobes of the 



common L. hians of our own coasts being very numerous, and of 



a bright orange colour. In many genera — e.g. Unio, Mactra — 



this sensibility to touch appears to be shared by the whole 



mantle border, although it is not furnished with any special 



fringing. The ' arms ' of the Cephalopoda appear to be keenly 



