REPORT OF COMMISSIONERS OF INLAND FISHERIES. 145 



2. That they are caused by injuries sustained after mouhing. 



3. That they are regenerative products. 



But there is considerable divergence of opinion regarding the 

 relative importance of these different theories. 



Faxon, in discussing his case of "duplicate" chela in Homanis, 

 which resembles somewhat specimen No. 5, of our list, remarks that 

 "whether this monstrosity be congenital, or the result of injuries 

 received later in life, I can not tell" (p. 263); although later, when 

 referring to this same case he adds, that " it is very probable that we 

 are dealing with a monstrosity which is not the result of injury" 

 (p. 267). Again, in regard to another case, a double index and two 

 dactyls (Plate I, Fig. 13), he thinks that "one can easily believe that 

 this is % congenital monstrosity" (p. 260). A fair interpretation of 

 Faxon's conclusions seems to be that he is inclined to consider all 

 cases of duplicate or triple chelae as congenital in their origin, while 

 he considers that simpler deformities, as, for example, specimens 1 

 and 2 of our list, " are more naturally explained as malformations 

 arising from injuries received after moulting" (p. 260). 



Bateson evidently gives least importance to the second and third 

 theories, for, in regard to this question, he says: "A good many 

 authors from the time of Rosel von Rosenhof onward^ have said 

 that these cases are a result of injury, or of regeneration after injury. 

 For this belief I know no ground. It should be remembered as an 

 additional difficulty in the way of this belief, that when the limb of 

 a crab or lobster is injured it is usually thrown off bodily, while the 

 extra parts most often spring from the periphery of the chela" 

 (p. 526). 



Andrews, in discussing his case of " an aberrant limb in a crayfish,'* 

 states that " The appearance of the limb suggests a new growth fol- 

 lowing some injury in which the material for claw making was partly 

 severed and displaced." As. to when this injury may have occurred, 

 he merely suggests that it " might happen, we can suppose, not only 

 in the egg and in the young, but in the adult, especially at the 

 periods of shedding when the interior of the claw is soft and the blood 



