THE AMERICAN LOBSTER. 14. r ) 



The monstrosities noticed in the chelipeds of the lobster are mainly the result of 

 a secondary outgrowth from one of the two terminal joints. Rarely the appendage is 

 duplicated or triplicated ; a case of the crayfish is reported with three extra claws 

 (see Bateson, p. 537). In some cases the extra appendages are perfectly formed, while 

 in others deformation has been carried to excess, resulting in irregular branching 

 processes or grotesque contortions. Injuries to the claws are excessively common, 

 while duplication of parts is rare. Defective or deformed claws, the result of injuries 

 (see figs. 194, 198) in different stages of repair, are met with every day by dealers, 

 while thousands of lobsters may be examined without meeting a single case of repeti- 

 tion or duplication of parts. 1 



If the tips of the claws are snipped off near the articulation of the dactyl, the 

 lost parts are restored (see p. 105) as we have seen at the next molt. This restora- 

 tion is often perfect, but not always so. The condition seen in fig. 198 might have 

 been caused by a pinch and arrest of growth while the claw was soft (before the last 

 molt), or by the unequal growth from a stump, the end of the propodus haviug been 

 cut off by an enemy just before the shell was cast. In the latter case the member 

 could be only partially restored, and unequal growth would account for the distortion. 



The dactyl shown in fig. 104 has probably had a similar history. All such cases 

 are the results of regeneration after injury. This can not be said of such a specimen 

 as that represented by fig. 189, where the dactyl bears upon its inner margin near the 

 tip a small conical prominence. This is smooth and is separated from the tip of the 

 dactyl by a shallow groove, as if there had been a normal bifurcation or division at 

 this point. What the primary cause of such a growth or swelling may be is not known, 

 but it is impossible to suppose it to be the result of injury. 



With the appearance of such a simple outgrowth a progressive series of changes 

 seems to take place with every molt, such as is illustrated by figs. 189-193, plate 47. 

 With the growth of the animal, the superadded part, whether it be upon dactyl or 

 propodus, seems to be shifted at each molt farther aud farther back upon the claw, and 

 meantime, in most cases, to uudergo fission in a vertical (figs. 190,191) or somewhat 

 oblique plane (figs. 187, 188). This fission apparently proceeds until one or both of the 

 supernumerary dactyls are entirely separated (tigs. 192, 193). The opposing edges of 

 these become gradually toothed, so that each is almost an exact copy of the original 

 (see especially fig. 193, plate 47). According to the principles laid down by Bateson, the 

 part which is nearer the original joint corresponds with the appendages on the oppo- 

 site side — that which is farthest away with those on the same side of the body. This 

 is not strictly true in such a case as that shown in fig. 19G, where the supernumerary 

 parts do not face each other, aud in some cases the repeated part is single, not double. 

 In fig. 190 a short row of teeth marks the median plane of division and the opposing 

 surfaces of the incipient fingers are also toothed. In tig. 191 the outgrowth is divided 

 nearly to its base into two secondary processes, each of which resembles the joint of 



'In 2,657 lobsters captured at Woods Hole, Massachusetts, from December to June, 1893-94, but 

 one case of repetition or formation of extra parts in the large claw occurred. No account was kept of 

 injuries, but in the months of December and January 7 per cent of all lobsters caught (54 in a total 

 of 725) had thrown off one or both claws. (See p. 103.) 



A man who had been engaged in the business of canning lobsters for a score of years in Maine 

 told me. that he had at one time nearly a bushel of deformed claws, which lie had collected in the 

 course of his experience. 



F. C, is. 1895—10 



