298 Mr. C. Speiice Bate's Notes on Crustacea. 



branchial chamber and extending along the anterior edge of the 

 tirst abdominal ring, precludes the admission of water into the 

 cavity occupied by the thoracic viscera. 



But the above is not the only purpose for which this imperfectly 

 developed pair of legs are made available. The extremities besides 

 being prehensile are more or less ciliated, forming a small brush : 

 with these I have seen Pagurus Bernhardus, while lying upon its 

 back half in and half out of its abode, mop and cleanse every 

 joint in succession, stopping now and then to wipe the brush in 

 the pedipalps with the greatest care. 



The absence of the Habellte from the branchial chamber is a 

 feature peculiar to the Anomoura, a fact valuable as assisting to 

 estabUsh the position of doubtful species, and which I would here 

 draw attention to, together with the fifth pair of legs being at- 

 tached to an annular segment distinct from the carapace, as 

 strongly supporting the opinion of Prof. Bell, who, in his ' Hi- 

 story of the British Crustacea,' places the Galatheans among the 

 Anomoura, in which arrangement he differs from Prof. Milne- 

 Edwards, who classes them among the Macroura. 



On the Development of the Shell of Crabs. 



V. From the period of leaving the ova to that of old age, 

 crabs at certain periods throw off their skins : when in the larva 

 state this is done every few days; as the animal grows older 

 weeks intervene, and then months, until lastly the exuviae are 

 cast but once a year, and probably when it is getting old they 

 may not be shed so often. 



But whether it be during the larva state or that of the adult 

 crab, the process of development under which the shell is pro- 

 duced must be one and the same. Immediately above the heart, 

 a pulp consisting of nucleated cells, areolar tissue (and blood- 

 vessels ?), is formed, extending to the internal surface of the shell, 

 from which it is separated by a layer of pigment which gives 

 colour to the new formation. Towards the base, that is, imme- 

 diately above the heart, the cells are uniformly large and distinct, 

 as represented in PI. X. fig. 1, while an areolar tissue ramifies 

 throughout the whole. As advance is made from the base, cells 

 of less size mix with them, which increase in number as they di- 

 minish in diameter until they approach the layer of pigment, 

 immediately beneath which they adapt themselves by mutual 

 pressure into a polygonal form. The pulp extends over the whole 

 periphery of the crab immediately beneath the shell, the thick- 

 ness of the pulp decreases with the distance from the centre, and 

 the larger cells become fewer in number, the mass being chiefly 

 made up of the smaller cells which become the secreting organs 



