PURPURA. 279 



said by Linne to eat the dead fish left in fishermen's 

 nets. I have seen it busily feeding on Balanus bala- 

 no'ides, its strong proboscis being inserted between the 

 opercnlar valves of the barnacle. According to Mr. 

 Osier, it also devours Littorince, Trochi, Natica, and 

 even its own kind. From what I have observed of the 

 mode by which it perforates the shell of a mussel, I am 

 inclined to agree with Mr. A. Hancock that it uses its 

 tongue. The siliceous spines with which this organ is 

 closely studded would scrape a hole in any layer of car- 

 bonate of lime, however compact. I cut off the end of 

 the proboscis of a Purpura, while it was attacking a 

 mussel ; the part thus lopped still remains in the hole, 

 with the front of the tongue exposed. The hole is 

 shaped like an inverted cone, and exhibits under the 

 microscope extremely fine scratch-like striae, as if caused 

 by the rasping action of the lingual apparatus. I believe 

 the movement to be rotatory, because the sides of the 

 hole are quite even. The process is an extremely slow 

 one. Mr. Osier states that, after watching for some 

 hours a Purpura attached to a limpet, he found the per- 

 foration incomplete; and Mr. Spence Bate and Mr. 

 Bretherton noticed that it took two days to get through 

 the shell of a moderate-sized mussel. It does not ap- 

 pear that the prey is destroyed by any poisonous secre- 

 tion of the whelk, after it has gained access to the 

 interior. The proboscis is at first thrust into the hole 

 which it had drilled, and the whelk eats in that way ; 

 but when, from the death of the mussel or limpet, the 

 former gapes or the latter separates from the rock, the 

 Purpura devours the remainder by the natural opening. 

 Perhaps they exercise some abstinence in the winter and 

 early spring, to make up for their continual gormandi- 

 zing during the warmer portion of the year. Mr. Peach 



