220 



LIFE, IN ITS INTERMEDIATE FORMS. 



would furnish a most interesting and instructive lesson in 



physiology. 



The broad plates which expand like a fan at the tail of 

 the Prawns and Lobsters, form their great resource for 

 swifc and sudden locomotion. The common Lobster is 

 said to be able to dart back by this means thirty feet, with 

 the fleetness of a bird on the wing ; and when we think 

 of this feat, we must not forget the great density and 

 resistance of such a medium as water, in which it is 

 accomplished. The existence of these plates, and the 

 great development of the abdomen which carries them, 

 distinguish these from the proper Crabs, which have 

 no terminal plates, and in which the abdomen is re- 

 duced to a thin flap bent under the body and pressed 

 close to it, except when it is forced out of place by 

 the spawn, which the females deposit between it and the 

 thorax. 



Some of the Crabs have the power of swimming, but 

 it is by a very different mechanism from that of the Lob- 

 sters; and it affords us one of the many examples which 

 the naturalist is constantly meeting with, of the infinite 

 resources of the wisdom of God in creation. In the com- 

 mon eatable Crab {Cancer pagurus), with the exception of 

 the foremost pair of limbs, which are expanded into power- 

 ful grasping claws, all the feet are terminated by a short 

 sharp-pointed toe. But we have some species common on 

 our shores (Portunus, #c.), in which the hindmost legs have 

 the last joint dilated into a broad, thin, oval plate, which 

 being fringed, as are also the other joints, with stiff hairs, 

 constitute oars, and being worked in a peculiar manner, 

 row the animals swiftly to and fro, at the surface or through 



