144 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



smaller than the other ; a small tubercle on upper side of propodus, on outer margin, 

 near carpus. There is considerable variation in the number and prominence of these 

 processes, particularly the marginal ones. 



Cutting -claw; Six marginal spines on propodus, second and fifth depressed; other 

 processes present, as in corresponding claw. 



Abnormal Variation. — (1) Female; length, 10J inches; hard shell; cutting- 

 claws on both sides similar; Woods Hole, Massachusetts, March, 1894. 



Bight cutting-claw: Small tubercles of propodus, near uactyl, wanting. 



Left cutting-claw: Transverse scar-hke groove on propodus, at level of articulation 

 •of dactyl ; one small tubercle on upper surface of propodus, near dactyl ; two very minute 

 ones below; five marginal spines, third bent inward, rest turned forward and upward. 



(2) Female; length, 10£ inches; hard shell. 



Right cutting-claw: Five marginal inner spines on propodus, third depressed; no 

 small tubercles near joint of dactyl present. 



Left cutting claw: A little smaller than right; 5 marginal spines, none depressed; 

 one small tubercle on lower side of propodus near dactyl. 



(3) Male; length, 10 inches; hard shell; both claws relatively small, having been 

 regenerated; length of propodus, 3jf inches. (Plate 14, fig. 19, from photograph.) 



Right cutting-claw: Seven marginal spines, second and fourth depressed; one 

 small tubercle on under side of propodus, near dactyl. 



Lieft, cutting-claw: Five marginal spines, second depressed ; one very small tubercle 

 on upper side of propodus near dactyl; two very minute ones below. 



There seems to be about as much variation as regards the details here mentioned 

 in normal symmetrical claws as in the abnormal symmetrical ones, and it is probable 

 that in either case the conditions met with are to some extent congenital. 



DIVISION AND REPETITION OF APPENDAGES. 



The curious monstrosities which occur in the appendages, particularly in the large 

 claws of the lobster, have attracted the attention of naturalists for a long time. They 

 were noticed by Von Berniz (17) over two hundred years ago, and some good figures of 

 the deformed claws of the crayfish were published by Eosel in 1755 (168). A careful 

 review of crustacean deformities, concerning the lobster in particular, was given by 

 Faxon in 1881. His paper was accompanied by valuable figures and a bibliography 

 (66). The general subject of variation as it affects the appendages of arthropods has 

 been recently treated in a masterly manner by Bateson in his invaluable work on 

 variation. 1 The variations which concern the Crustacea, particularly the decapods, are 

 fully described and illustrated, with references to the abundant literature. Bateson 

 shows that in most of the cases of supposed duplication of limbs in both insects and 

 Crustacea the extra parts are double instead of single, as where two dactyls are 

 formed at the extremity of the claw instead of a complete claw consisting of dactyl 

 and propodus. He has also formulated certain principles according to which super- 

 numerary appendages make their appearance in secondary symmetry. If the normal 

 appendage which bears the extra ones is a right leg, "the ne rer of the extra legs is 

 a left and the remoter a right." 



1 Materials for the study of variation treated with especial regard to discontinuity in the origin 

 of species, by William Bateson, 1894. 



