284 NATURAL HISTORY. [CH. XXI. 



" For s.ome time before the old shell was cast off, 

 preparations had been making for forming a new 

 one. The membrane which lined the shell had been 

 acquiring greater density, and had already collected 

 a quantity of liquid materials proper for the consoli- 

 dation of the new shell. These materials are mixed 

 with a large proportion of colouring matter, of a 

 bright scarlet hue, giving it the appearance of red 

 blood, though it differs totally from blood in all its 

 other properties. As soon as the shell is cast ofl, 

 this membrane, by the pressure from within, is sud- 

 denly expanded, and, by the rapid growth of the soft 

 parts, soon acquires a much larger size than the for- 

 mer shell. Then the process of hardening the cal- 

 careous ingredient commences, and is rapidly com- 

 pleted ; while an abundant supply of fresh matter is 

 added, to increase the strength of the solid walls 

 which are thus constructing for the support of the 

 animal. Reaumur estimates that the lobster gains, 

 during each change of its covering, an increase of 

 one fifth of its former dimensions. When the ani- 

 mal has attained its full size, no operation of this 

 kind is required, and the same shell is permanently 

 retained. 



" A provision appears to be made, in the interior 

 of the animal, for the supply of the large quantity of 

 calcareous matter required for the construction of 

 the shell at the proper time. A magazine of carbo- 

 nate of lime is collected, previous to each change of 

 shell, in the form of two round masses, one on each 

 side of the stomach. In the crab these balls have 

 received the absurd name of crabs' eyes ; and during 

 the formation of the shell they disappear. 



" It is well known, that when an animal of this 

 class has been deprived of one of its claws, that part 

 is, in a short time, replaced by a new claw, which 

 grows from the stump of the one which had been 

 lost. It appears, from the investigations of Reaumur, 

 that this new growth takes place more readily at 



