60 Royal Suciety : — 



vascular and nervous layer that the contents of the hair-canals and 

 of the corresponding canals in the shell are especially connected. 

 This can be readily seen in parts where the shell is thin, as in the foot- 

 jaws for example. In a section made in such a situation, the canals 

 leading to the hairs will be found to be often nearly as large as the 

 bases of the hairs to which they correspond. They are lined by a 

 thick membrane, which invests the cup-shaped cavity in which the 

 hairs are implanted, and becomes so closely connected with the bulb 

 of the hair itself, that it is often dragged out with it when the hair 

 is pulled out. The cells aud other elements of the deeper layer 

 of the internal integument fill up the canal and pass on into the 

 hairs. 



Where the shell is thick, as in the claw of a lobster, the sheaths 

 which are connected with the hair-bulbs and line the shell-canals can 

 be demonstrated in the manner adopted by Mr. Tomes to show the 

 existence of the dentinal fibres. If a section of a part of the shell or 

 the claw where the hairs are implanted, and which has beesi previously 

 softened in dilute acid, be torn through, the sheaths will usually be 

 dragged out, and will be seen projecting from the torn edges, their 

 contents often remaining in them. The connexion of the inner in- 

 tegument with these sheaths may be seen in sections of the claw with 

 the integument still adhering to it, when on carefully tearing away the 

 latter, its prolongations into the sheaths will be dragged out. That 

 the hairs have some especial and important connexion with the inner 

 vascular and nervous layer of the integument of the lobster's claw and 

 elsewhere, seems probable from the observations made by the author 

 on the contents of the claw. The terminal moveable piece, the pollex, 

 and the prolongation of the metatarsus which it opposes, the index, 

 do not contain muscular fibre, but are filled entirely by a soft pulpy 

 mass of corium. The nerves of the limb are large, but only some 

 small branches will be found to go to the muscles; the principal nerves 

 pass on and terminate in the pulp which fills the opposing pieces of 

 the claw. The author believes that it is the office of the hairs to 

 establish a communication between the outer surface and this inner, 

 and no doul)t highly sensitive pulp, and that this is rendered still 

 further prol)aljle by the compaiison of the claws on the two sides. 

 In the smaller claw the edges are sharp, and have fine tubercles 

 along their margin ; and the hairs are }»laced in a regular series of 

 short tufts on each side of the tubercles, beyond which they do not 

 project. But on the larger crushing claw, the tubercles are massive, 

 and no hairs are seen projecting above the surface. If, however, a 

 section be made, it will be seen that a conmiunication is esta- 

 blished between the inner pulj) and the surface by means of an abun- 

 dant series of canals which terminate in bulbous extremities, sometimes 

 projecting beyond the surface, sometimes lodged in depressions in the 

 shell. This arrangement may be found in other parts; and in the 

 cral)'s claw, where the tuijercles are deficient, these hairless pulp- 

 cavities almost entirely replace the hairs. 



Here, then, lodged within the densest part of the shell, is a struc- 

 ture richly supplied with nerves, shut off from other {)arts of the 



