tacgart] 



CRAYFISH STLDY' 



109 



What is the order of movement, or is there any order? How does it 

 swim forward? How backward? How does it turn over if put 

 on its back ? 



11. What is the function of each of the various appendages? 

 How is it adapted to its particular function ? 



12. One or both of the great claws is often lacking, or one 

 may be smaller than the other. Children always seem to notice 

 this and raise the question how and why. H small crayfish are 

 used which moult frequently the process of the regeneration of 

 the claws is easily watched and is usually something quite new 

 and wonderful. 



13. When the females are found with eggs the pupils can 

 easily find evidences of maternal care in the treatment of the 

 eggs and young. 



14. If material is plentiful the children can sort the animals 

 into diflferent piles according to any standards they choose, and 

 at the end it will be found that the only constant characters — the 

 characteristics which separate species and the ones employed by 

 systematists — have been used by the pupils in distinguishing the 

 various kinds. 



l"). The comparison of crayfish to discover the individual 

 variation in size, color, shape and activity due to sex, environment 

 and other causes, is well worth while when done with under- 

 standing or as a means of answering problems that naturally arise. 



