lO UNIVERSITY OF MISSOURI STUDIES [^98 



The general discussion of the theoretical considerations and 

 the criticism of the above-mentioned experiments, together with 

 a consideration of their relation to the results of my own experi- 

 ments, are to be found in the latter part of this paper. 



II. METHODS. 



In the fall of 1896, I began a series of experiments and ob- 

 servations upon the regeneration of crayfish of the genus Cam- 

 harus. Two species were used, C. virilis and C. gracilis, and 

 since the beginning of my experiments I have continually kept 

 crayfish under observation. Great difficulty has been expe- 

 rienced, however, in keeping the animals alive until the comple- 

 tion of the process of regeneration, and this has, in some degree, 

 interfered with the entire success of individual experiments. Af- 

 ter many trials I finally devised, if not an entirely, at least a 

 fairly satisfactory method of taking care of them. Before any 

 definite and conclusive results can be obtained it is necessary 

 that the crayfish should pass through at least one or two moults, 

 for otherwise an appendage is never completely regenerated. 

 Very often the crayfish dies in the act of moulting, or, if it lives 

 through the process, dies soon afterwards. 



When I first began the experiments, I kept several crayfish 

 in the same compartment, fed them nearly every day and also 

 changed the water on them daily, never allowing the water to 

 completely cover them. I learned by experience that I could 

 neither keep several together nor feed them each day. When 

 several were placed in the same dish the larger ones would 

 sooner or later eat the smaller ones, or when one moulted it was 

 almost certain to be attacked in its helpless condition and de- 

 voured. There were several disadvantages in isolating individ- 

 ual animals, and I therefore tried different schemes for keeping 

 them together. At first they were put into a large wire cage 



