CRUSTACEA. 203 



which remain soft and undefended by the crust. 

 But we have seen a swimming-crab (Matuta) hold its 

 prey in one claw, while with the other it picked off 

 morsel by morsel of the flesh, and conveyed it to its 

 mouth in a manner which sufficiently evidenced the 

 sensation of touch in these organs; and we have 

 watched a beautiful West Indian crab (Groniopsis 

 ruricola) feeding itself in the same manner, picking 

 up, now with one claw, now with another, minute 

 atoms of food from the surface of the mud over 

 which it marched, with a rapidity and a precision 

 which seemed to indicate that a very delicate sense 

 of touch resided in those shelly claws. MR. GOSSE. 



The periodical casting of the shell, or moulting, 

 is a very remarkable feature in the economy of these 

 creatures. Frequently during their lives their hard 

 and shelly covering is cast off in one unbroken piece, 

 so as to present an exact counterpart of the perfect 

 animal. Every part of the integument is thus 

 renewed, nothing is wanting in the cast-off skin, the 

 antennae, the jaws, the eyes, are all there, every hair 

 is represented by the case which enclosed it. Even 

 the shelly plates from which the muscles originate, 

 the tendons by which they are attached to the shell, 

 the internal skin of the stomach, and the teeth which 

 are hidden there, are found connected with the re- 

 jected shell ! 



The pressure of the old shell being removed, the 

 animal suddenly increases in bulk, the new skin, as 

 yet soft and flexible, allowing at first of great expan- 

 sion ; but it rapidly hardens, a stock of shelly matter 

 having been for some time accumulating in its 

 stomach, in the form of two hard balls, commonly 

 called crabs -eyes. This substance is supposed to be 

 taken up and distributed to the surface, so that when 

 the new crust has again acquired consistence, these 

 concretions are no longer found. The whole process 

 occupies from one to three days. The supposition 

 that the moulting in these animals takes place every 

 year, must probably be restricted to the period of 



