THE LOBSTER AS A TYPE OF CRUSTACEA 29 



The two large claws of the Lobster (see Plate I.) 

 are not quite alike in size or in shape. The smaller 

 of the two has the inner edges of the fingers sharp 

 and set with saw-like teeth ; the larger has the 

 fingers armed with blunt rounded knobs. The 

 larger claw is adapted for crushing the shells of the 

 animals on which the Lobster feeds, while the smaller 

 serves for holding and tearing the prey. In the 

 Lobster, as in many of the higher Crustacea in which 

 this asymmetry occurs, the larger claw may be 

 indifferently on either side of the body. There are 

 certain cases, however, among Crabs where the large 

 claw is constantly on the same side of the body, or, 

 in other words, all the individuals are either right- 

 handed or, more rarely, left-handed. 



If a Lobster be caught by one of its claws or by a 

 leg, it very readily parts with the limb in its struggles 

 to escape ; and if one of the limbs be crushed or 

 otherwise injured, it is often cast off by the animal. 

 The separation always takes place at the same point, 

 near the base of the limb, and is not simply due to 

 the limb breaking at its weakest part. It is a reflex 

 act, brought about by a spasmodic contraction of 

 some of the leg muscles. At the place of separation, 

 corresponding to the junction of the second and 

 third segments of the limb, which, as already men- 

 tioned, are soldered together, the internal cavity is 

 crossed by a transverse partition, having only a small 

 aperture in the centre through which the nerves and 



