THE MODE OF REPRODUCTION OF, &c. 75 



period. Wounds of the body in general prove speedily fatal, if 

 they penetrate deeply, but if otherwise, a cicatrix only is formed, 

 which remains until the casting of the shell, when the new shell 

 takes on all the characters and appearance of the old one, before 

 it met with the injury. When the animal is weak and unhealthy, 

 and in that state meets with any severe injury of a limb, it is un- 

 able to throw it off at the usual place, and consequently very 

 soon dies from loss of blood ; but when strong and vigorous, it is 

 enabled to throw the injured limb off with little apparent pain or 

 exertion. It is a well known fact, that these animals can throw 

 off their limbs when seized by them, and also from several other 

 causes, to which it is unnecessary to allude at present. 



When the crustacean does throw off a limb voluntarily, it will 

 be found on examination that this is always effected at one spot 

 only, near to the basal extremity of the first phalanx. This part 

 of the phalanx is very much contracted for the length of half an 

 inch, or a little more, in the common edible crab. The whole 

 of this portion is filled with a fibrous, gelatinous, glandular look- 

 ing mass ; the organ which supplies the germs for future limbs. 

 On looking closely into the surface of this body, we find that it is 

 divided into two unequal parts, by means of a transverse line. 

 The basal or proximal part of this body is the smallest. On 

 tracing this line towards the shell, we find that it runs into it, as 

 it were, and forms, instead of one line, two, by which means a 

 very thin ring is formed, and this ring is also found to run com- 

 pletely round the limb, being marked externally by means of a 

 thin band of small scattered hairs. By dissection this line can 

 be traced into the substance of the organ of reproduction, 

 and is found in this way to be the exact spot where the limb is 

 generally thrown off. Through the long axis of this, and near 

 to one edge, a small foramen exists for the transmission of the 

 blood-vessels and nerve. The microscopic structure of this gland 

 or organ is extremely beautiful. When a thin transverse section 

 is made, and placed under the microscope, it is found to present 

 the following appearances : The foramen, for the transmission 

 of the vessels and nerves, which was distinctly seen with the 

 naked eye, is obscured on account of the pressure arising from 

 the glass plates, but its situation can be still distinctly made out 



