82 A. B. DAWSON. 



SUMMARY. 



1. An abnormal lobster cheliped is described in this paper. 

 The abnormality consists of a double extra crushing claw arising 

 from the meropodite of a claw of the nipping type. 



2. The conditions found here are shown to present an exception 

 to Bateson's rules of secondary symmetry. 



3. The primary member of the so-called triple claw was found 

 to be of the same character as the corresponding appendage of 

 the opposite side, furnishing an exception to the normal condition 

 of asymmetry. 



4. Pigmentation was reversed in the double extra claw. 



5. There is some evidence in favor of the view that there is 

 a definite relation between the reversal of pigmentation and the 

 doubling of the extra appendage. 



LITERATURE. 

 Bateson, W. 



'94 Materials for the Study of Variation, Treated with Especial Regard to 



Discontinuity in the Origin of Species. London. 

 Cole, L. J. 



'10 Description of an Abnormal Lobster Cheliped. BIOLOGICAL BULLETIN, 



Vol. 18, pp. 252-268. 9 figs. 

 Emmel, V. E. 



'07 Regenerated and Abnormal Appendages in the Lobster. _3?th Annual 



Report Com. of Inland Fisheries, R. I., pp. 99-152, PI. 1-9. 

 Faxon, W. 



'81 On Some Crustacean Deformities. Bull, of Mus. Comp. Zool., Vol. 8, 



No. 13, PP- 257-275, Pis. 1-2. 

 Harrison, R. G. 



'17 Transplantation of Limbs. Proc. Nat. Acad. Sci., pp. 245-251. 

 Reed, Margaret A. 



'04 The Regeneration of the First Leg of the Crayfish. Arch. Entw.-Mech. 

 Bd. 18, p. 307. 



