144 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



But the regeneration of two crusher claws can not be brought into 

 either of these two categories; for, of course, they cannot be 

 explained as due to a "retarded differentiation," nor does it appear 

 that they may be regarded as a " reversion to a phylogenetically later 

 type." It is apparently impossible to interpret such a regeneration 

 as a case of "compensatory regulation" in Zeleny's ('05) sense, for 

 the regenerated chelse are almost identically similar both in size and 

 form. Nor is it clear that they can be brought under the category 

 of "revisal" phenomena, if by this term we imply a reversed order of 

 asymmetry. At present, therefore, this phenomenon must rather 

 be described merely as the substitution by regeneration of a " crush- 

 ing" claw in place of an original " nipping" claw. 



I have no suggestion to offer in explanation of these two cases of 

 the regeneration of similar crusher chelse. Evidently the regenera- 

 tive cells in the stump remaining after autotomy may have the 

 potentiality of either a "crushing" or "nipping" claw. But what 

 factors determined that a claw of the crusher type be produced is 

 another question. Wilson's ('03) suggestion for Alpheus, "that the 

 initial factor (Auslosung) that sets in motion the complex process of 

 differentiation of which either side is capable is primarily only a 

 difference in the amount of material on the two sides" (p. 210), can 

 hardly apply here, for the chelse were both removed autotomously 

 and at the same time, consequently there seems no reason to believe 

 that the "amount of material" was unequal on the two sides. As 

 far as the present data goes, the regeneration of similar "crushing" 

 claws still remains unexplained. 



3. Regarding the Origin of Abnormal Appendages. 



a. Discussion of Theories ivith Special Reference to the Regeneration 



Theory. 



Three possible theories have been proposed for the origin of ab- 

 normal chelae among Crustacea: 



1. That they are congenital or inherited. 



