ipi] REGENERATION OF CRAYFISH APPENDAGES 3 



the regenerated appendage after a moult has taken place, for 

 previous to a moult new legs are not exactly like the old ones 

 "except in size ;" constrictions merely appear in the place of true 

 joints, and the movements are far from similar to those of a 

 normal leg. It is difficult to understand what difference he ex- 

 pected to find by not feeding the crayfish, for the only probable 

 effect would be to retard the regeneration. 



Reaumur also noticed that the length of time required for 

 the production of new appendages was dependent upon a num- 

 ber of conditions. The growth was more rapid in warm than 

 in cold seasons, and when the legs were broken off in winter 

 they did not grow again until summer. He also cut ofif the 

 ''tails" of crayfish, but states that no regeneration took place and 

 that the animals invariably died a few days after the operation. 

 His attempt to explain the regenerative process is one of the 

 earliest explanations offered. He supposed that scattered 

 throughout the limbs are little "eggs" containing the germs of 

 parts of new limbs and that when an appendage is broken off the 

 juices which go to nourish this limb are then directed to the de- 

 velopment of the "eggs" containing parts of new limbs. He 

 saw that before such an explanation would be adequate there 

 would have to be more than one "egg" of the same kind, for a 

 regenerated leg can be broken off and another one regenerated 

 in its place. In fact the process can be repeated a number of 

 times, and obviously there would have to be reserve germs for 

 an indefinite number of regenerations. Such an explanation 

 immediately reminds one of Bonnet's theory (i77o) of head and 

 tail stuffs and their influence upon germs, except that Bonnet did 

 not suppose specifically diiferent germs at every level. Compare 

 also Weismann's doctrine of determinants. 



Chantran ('7i) in the study of the growth and devel- 

 opment of crayfish incidentally made some observations upon 



