98 ZOOLOGY 



caught off the Livoniaii coast, even some distance out at 

 sea. Individuals of an American species have been taken 

 from a mineral spring impregnated with sulphur and 

 magnesia at a temperature of 70 Fahr. (21 Cent.), 

 while several kinds of the American "burrowing' or 

 " chimney "-forming species have been found in meadows 

 and clay bottoms, often at great distances from streams. 

 Certain species that are blind inhabit caves only. In 

 England, according to Huxley, "in granite districts, and 

 others in which the soil yields little or no calcareous 



ty 



matters to the water which flows over it, crayfishes do not 

 occur. They are intolerant of great heat or of much sun- 

 shine ; hence they are most abundant in those parts of 

 rivers which flow east and west, and thus yield the most 

 shade from the midday sun." 



The food of the crayfish is very varied ; it may be living 

 or dead, animal or plant. On account of the need of 

 calcareous matters in the food, crayfishes are especially 

 fond of the stoneworts (Chara) and various succulent 

 roots, like the carrot. It is said that crayfishes sometimes 

 make excursions inland in search of plant food. They 

 likewise devour shells of snails, their own cast-off skins, 

 and occasionally each other, shell and all. 



There are two great groups or subfamilies of cray- 

 fishes. One, restricted to the Northern Hemisphere, is 

 found in Europe, Asia, and North America. The other is 

 found in the Southern Hemisphere, in Australia, Tasmania, 

 New Zealand, Fiji Islands, Madagascar, and South America. 

 No crayfishes have been found on the continent of Africa, 

 or in the rivers of northern Asia that flow into the 

 Arctic Ocean, or in those of southern Asia. These Asiatic 

 rivers are populated by fluviatile crabs, to which the cray- 



