PRESH-WATER CRUSTACEANS. 285 



be covered with, well-washed gravel . and large stones, the 

 latter so placed that there will be an island on to which the 

 Crayfish can climb, and retreats into which they can retire. 

 The water need not be more than 4in. deep. It wiU not be 

 wise to introduce any aquatic plants, for the Crayfish would 

 destroy them all. These creatures, while in captivity, will 

 eat raw meat, tadpoles, dead fish, moUuscs, garden-worms — 

 in fact, almost anything of an animal nature. No food should 

 be left ia the aquarium which the Crayfish have refused to 

 eat; but, notwithstanding all care in this respect, the water 

 will require changing from time to time. 



It is a very interesting sight to watch these creatures 

 cast their shells. This exuviation is necessary, for the armour 

 of crustaceans does not stretch as the animals grow. Tor 

 some days previous to this important operation. Crayfish 

 lose their usually very keen appetites, and appear to take 

 no food at all. This fastiug causes the body to shrink, and 

 thus the moult is facilitated. The casting of the shell takes 

 about half an hour, and after it is cast the animal is very 

 exhausted — so much so, indeed, that occasionally it dies, 

 especially when the exuviation takes place while the creature 

 is in captivity. The moulting is particularly complete, even 

 to the eyes, antennae, and the lining membrane of the 

 stomach. 



Crayfish will sometimes breed in confinement. Unlike most 

 , of their relatives, the young, when they leave the eggs — 

 for Crayfish are oviparous — very much resemble their parents. 

 Crayfish inhabit the rivers of different parts of England, 

 particularly those which have unusually gravelly and rocky 

 bottoms, and are fond of hiding in holes in the banks or 

 among the rooks and stones. They are generally caught by 

 means of nets, in which pieces of raw meat have been 

 placed. 



A Crayfish may be described as a small fresh-water lobster 

 of a green coloui-. When taken out of the water and held 

 in the fingers, it flaps its tail with great vigour. Astaci 

 should not be carried from place to place in water, but in 

 damp water-weeds. 



