208 Mr » hroderip on the Habiis of Paguri. 



of Olivier, I am inclined to believe.) Two specimens are in my posses- 

 sion ; one of which is housed in a very large young shell of Pteroceras 

 truncatum, the other (nearly a foot long) is naked, and on examinino- the 

 under side of the tail of this, a great number of transverse rows of 

 acetabula are to be seen even without the aid of a glass. My friend 

 Dr. Bright has another naked specimen in which the same formation, 

 which must very much assist the hold of the Pagurus, is visible. 



Of the other Crustacea mentioned in Mr. De la Beche's letter I can at 

 present say nothing decisive. Some of them are evidently the common 

 land crabs: but that species which is described as haunting the borders of 

 the sea, almost within reach of the spray, but never entering it, and to 

 which submersion in vrater appears to be fatal, seems to be a beautiful 

 link between the sea crabs and those of the land. The periodical visits of 

 these last to the sea are well known as well as the distance which they 

 will travel, regardless of any obstacle, to attain their obJ€ct.f Almost all 



f Mr. Thompson m the interesting" paper where he gives his important disco- 

 very that the Crustacea Decapoda undergo a metamorphosis, shewing thatZoeais 

 not a perfect animal but the larva of the common crab (Cancer Pagurus), says, 

 " In their first and tender stage, they, (the Crustacea decapoda) are essentially 

 " and purely natatory animals, and no doubt possessed of corresponding 

 ** habits, swimming about freely and without intermission in search of appro- 

 « priate food ; in their perfect state, the greater number can no longer avail 

 " themselves of the power of swimming, but are furnished with pincers and 

 " feet almost solely adapted to crawling, so that they are now under the neces- 

 " sity of confining their excursions in pursuit of prey within more narrow 

 " limits. This curious piece of economy, explains what has ever appeared 

 ** paradoxical to Naturalists, viz. the annual peregrinations of the land-crabs 

 ** to the sea-side, which, although acknowledged to be true by several compe- 

 " tent observers, could never before be satisfactorily accounted for." Zoologi- 

 cal Researches and Illustrations, by John V. Thompson, Esq., F.L.S., Surgeon 

 to the Forces. Memoir I. p. 9. — ^Most of the authors cited in the text knew 

 that the objects of the land-crabs (Gecarcinus) in so pertinaciously going to the 

 sea at their appointed time was the business of laying, or, as some of them term 

 it, washing off their eggs, Labat thus describes the process i — " Les Tourlou- 

 *' roux y vont encore pour faire leurs eeufs, ce qui leur est fort ais6, car comme 

 " ils sont d6ja hors dg leurs corps attaches seulement aux poils de leur queue, 

 " ils ne font que la secoiier dans I'eau oti ils se baignent, et ces eeufs un peu 

 "plus petits que ceux des carpes, se d^tachent des poils qui les retenoient, torn- 



I 



