anurews] THE KEEPING AND REARING OF CRAYFISH 301 



Where a school provides two years work in biology, it will be 

 possible to have a class follow the same larva; to maturity; other- 

 wise each class must be content to see the maturity of young started 

 by the preceding class. To rear the young to maturity it is necessary 

 to keep them during the summer vacation and this will require some 

 attention, at intervals of a week or so, from an attendent or person 

 capable of following some few directions. Several broods of young 

 may be put into a sink or box two by four feet or more and eight or 

 nine inches deep, placed before a window so that aquatic plants will 

 thrive in it. A small stream of running water is necessary. The 

 tank should have two inches of mud and three of water in it and be 

 well stocked with Elodea, Chara or any other plants that will grow 

 under water. Snails, river clams, dragon-fly and other insect larvae 

 and Tubifex are good additions. 



The outlet pipe must be guarded by wire net and possible overflow- 

 ing prevented by periodical inspection. From time to time bits of 

 egg, meat, bread, or portions of freshly killed crayfish, should be 

 put in for food; but in this it is repetition rather than quantity that is 

 to be aimed at. 



In the autumn some few survivors should be on hand to greet the 

 pupils and if these young crayfish have been well fed they will be 

 sexually mature, even though but two inches long. If allowed to lie 

 torpid in cold water during the winter some of the small crayfish may 

 be expected to lay eggs the following spring though they will st 11 be 

 of the same small size. 



The complete life cycle is thus ended within twelve months and 

 while this is a long period in comparison with what may be chosen 

 amongst insects, yet for so large an animal it is but a brief time and 

 as far as it is followed by the pupil it will furni h opportunity for 

 training sustained interest in one complex object that illustrates 

 many fundamental phenomena of living things. 



