QO ANIMAL BIOLOGY 



less frequently. Concerning the age reached by crayfish 

 we know little except that they live at least several years. 

 Crayfishes are used for food quite extensively in Europe 

 and to a considerable extent in this country. 



Among the nearest allies of the crayfish are the lobsters. 

 The American lobster, Homarus americanus, which is 

 closely allied to the European species, is found on the 

 eastern coast of the United States as far south as Virginia. 

 It may reach a length of two feet and a weight of twenty- 

 five pounds. As it is a favorite article of food, it is caught 

 in great numbers so that the larger individuals are now 

 more rarely found. It is usually caught in a wooden cage 

 called a lobster "pot," which is so constructed as to allow 

 the lobsters to go in which they are induced to do to 

 obtain the bait but which prevents their escape. Owing 

 to the decreased yield of our lobster fisheries it has been 

 made illegal to sell lobsters of less than a certain length. 

 At various places on the coast, lobster hatcheries have 

 been erected. Here the eggs are kept in jars of running 

 water until they hatch, when the young are carried out to 

 sea. How greatly the supply of lobsters has been increased 

 by this method is a matter of great uncertainty. The 

 young lobster makes its first appearance in a larval form 

 very different Jrom the adult and passes through a long 

 metamorphosis before attaining its final form. 



Somewhat more distant relatives of the crayfish are the 

 various species of prawns and shrimps. These, like the 

 lobsters, are caught in large quantities for the gratification 

 of the human appetite. The hermit crabs are noteworthy 

 for their common habit of living in the coiled shells of 

 mollusks into which they can more or less completely 

 withdraw. The anterior part of the body and the anterior 

 appendages which are habitually exposed to the impacts 

 of the outer world are hard, but the abdomen which 



