JOINT APPENDIX No. II. 



Natural History of Crabs and Lobsters. — By Frank 

 Buckland, Esq. 



Having obtained during the late inquiry, and by other investigations, some 

 additions to the general knowledge of the natural history of Crabs * and 

 Lobsters, my Colleagues have agreed that I should have the privilege of 

 putting these facts together in a consecutive form, with a view of elucidating 

 the accompanying report. 



Crabst and lobsters may be said to correspond with insects, and to do much Anatomy of crabs 

 the same duties in the water as insects perform on land. Linnaeus formerly 

 included the crab, lobster, and crayfish with Arachnidas or spiders, under the 

 general division of insects. Even now a certain kind of crab, the " Skerry," 

 or " Corwick " of Cornwall (Maia Squinado), is called the " Spider Crab " or 

 the " Thornback Spider." 



As a watch case contains much delicate and complicated machinery, so does 

 the back shell or carapace of crabs and lobsters contain many highly com- 

 plicated and wondrous structures. Thus in the crab, we can see by dissection 

 the membrane which lines the carapace and covers the viscera, the large and 

 powerful heart, two sets of arteries, the gills or lungs, the mouth, the stomach, 

 the convoluted intestines, and the very large liver. The lobster is somewhat 

 similar in its anatomy. 



The general appearance of a crab or lobster when walking at his leisure is 

 very insect-like. In the] crab and lobster the skeleton is external ; they have 

 no bones at all ;{in fact they may be said to live inside their skeleton, or, if you 

 please, to be " Natural armour-clads," the joints in their harness being beauti- 

 fully adapted for offence and defence. This covering is composed of the skin 

 more or less hardened. This " dermo skeleton," when once complete, under- 

 goes little or no further change. It is adapted to the increasing size of the 

 body by being periodically cast and entirely renewed at such periods as the 

 body grows too large for its case : in fact crabs and lobsters grow by 

 *' moulting " their shells. % 



If the claw of a lobster be placed in strong nitric acid, a great effervescence Composition 

 takes place; this is caused by the solution of the phosphate and carbonate of ° she11, 

 lime of the dermo-skeleton in the nitric acid. In the lobster there is 60 per 

 cent, of carbonate of lime, and 14 per cent, of phosphate of lime. The animal 

 must, of course, secrete these mineral matters from the sea water. The shell 

 of the crab is not quite so readily soluble in nitric acid as the shell of the 

 lobster. When the nitric acid has done its work, and the effervescence has 

 ceased, the lobster's claw is found to be quite soft and flexible, like a wetted 

 glove finger, though still retaining its original shape. This substance, (the 

 skeleton of the animal), is composed of Chytine, the horn-like substance which 

 forms the elytra of insects. The firm horn-like covering of the wing of a cock- 

 chafer, is a good example of Chytine. I have examined the new and soft skin 

 of a crab which has just cast its shell ; it is about the consistence of thin brown 

 paper, and when burnt smells somewhat like horn. In fact this new skin 

 corresponds to an old skin out of which the earthy materials have been 

 dissolved by nitric acid. 



The skeleton of the crab has been described as being composed of three 

 ayers : the epidermis or cuticle, the rete mucosum or pigment, and the corium. 



* In Scotland crabs are called partans. 



t The crab has been promoted to form one of the signs of the zodiac. He represents the 

 month of June, because when the sun has come to this constellation he begins to go back- 

 wards after the manner of a crab. The crab thus got his promotion : when Hercules was 

 fighting against the Lernaeau hydra, a crab came out of the marshes and bit his foot ; and 

 Juno promoted him to be a constellation among the stars. 



% See further remarks on this, pp. 10, 11, and 19. 



