THE GROWTH OF THE CRAYFISH. 31 



liver (fig. 5, Lr) ; and, in the breeding season, the 

 ovaries of the females, or organs in which the eggs are 

 formed, are very conspicuous from the dark-coloured 

 eggs which they contain, and which, like the exoskeleton, 

 turn red when they are hoiled. The corresponding part 

 in a cooked lobster goes by the name of the " coral." 



Beside these internal structures, the most noticeable 

 are the large masses of flesh, or muscle, in the thorax 

 and abdomen, and in the pincers ; which, instead of 

 being red, as in most of the higher animals, is white. 

 It will further be observed that the blood, which flows 

 readily when a crayfish is wounded, is a clear fluid, and 

 is either almost colourless, or of a very pale reddish or 

 neutral tint. Hence the older Naturalists thought that 

 the crayfish was devoid of blood, and had merely a sort 

 of ichor in place of it. But the fluid in question is true 

 blood ; and if it is received into a vessel, it soon forms a 

 soft, but firm, gelatinous clot. 



The crayfish grows rapidly in youth, but enlarges more 

 and more slowly as age advances. The young animal which 

 has just left the egg is of a greyish colour, and about 

 one quarter of an inch long. By the end of the year, it 

 may have reached nearly an inch and a half in length. 

 Crayfishes of a year old are, on an average, two inches 

 long ; at two years, two inches and four-fifths ; at three 

 years, three inches and a half ; at four years, four inches 

 and a half nearly ; and at five years, five inches. They 



