278 BULLETIN OP THE BUREAU OF FISHERIES. 



seems highly probable that the reversal, which regularly takes place in Alpheus when 

 its great "hammer" claw is cut off, does actually occur, though but rarely, in the lobster, 

 or, rather, that a step in the process takes place, there being no immediate compensatory 

 change to restore equilibrium of the system of which the great claws form a part. Thus, 

 when a "club" claw is "shot" or amputated by the experimenter, a chela of similar 

 crushing type is usually regenerated in its stead, but rarely a toothed claw may appear. 

 There is a change in the appendage, bringing about an abnormal condition of symmetry, 

 but the process stops here, and we have as the result lobsters with similar toothed claws, 

 like the specimen illustrated in an earlier work (149). 



In like fashion the toothed claw of the lobster is usually replaced in regeneration 

 by a Umb of similar type, as is the rule with Alpheus, but in rare cases a "club" claw is 

 substituted, and we get a lobster with symmetrical crushing chelae, like the specimen 

 described by Doctor Caiman. This case is certainly much rarer than reversal from 

 crushing to toothed claws. There is the possibility that these abnormal conditions of 

 symmetry may be upset by a compensatory change in the appendage of the opposite 

 side, but there is no evidence at present that this ever takes place. 



When most of the preceding paragraphs on this subject were written I had not seen 

 Emmel's valuable paper on the regeneration of crusher claws following the amputation 

 of the normal asymmetrical chelae in the lobster. Accordingly, the statement that the 

 case reported by Doctor Caiman was "for the present essentially unique in the literature 

 of the subject" applied only to the fact of its occurrence in a state of nature or freedom, 

 the two other lobsters reported by Emmel and referred to above being regeneration 

 products resulting from amputations. 



In discussing the significance of the substitution of the "crusher "for the primitive 

 "toothed" type of claw, Emmel does not consider that any explanation is at present 

 possible, either on the basis of "reversal" phenomena or of "compensatory regulation," 

 and he thinks that we must be content at present with a record of the fact that sub- 

 stitution by regeneration takes place. I have endeavored merely to point out the 

 probability that in such forms as Alpheus and Homarus we are dealing with processes 

 which are essentially similar. 



CHANGES IN THE TOOTHED CLAW AT MOLTING. 



The adjustment of the blood supply in the big claws and the adaptation of their 

 tissues to the process of molting, in the course of which their great bulk of muscles is 

 pulled through the narrow ring at the base of the cheliped, are described in chapter iv. 

 We shall now consider the interesting changes in the armature of the toothed claw or 

 lock forceps, which are expressed at a given molt. 



The behavior of the spines of this weapon suggests the movements of a company 

 of soldiers at driU, and offers a striking illustration of that power of regulative control 

 which distinguishes living things. The peculiar alignment of the spines of the forceps, 

 by means of which its serrated jaws overlap, apparently effected by concerted but 

 reversed movements of the teeth, and the behavior of the large "lock" spine, which 

 gradually shifts to a position far out of line with its fellows, have already been described. 



