DESCRIPTION OF AN ABNORMAL LOBSTER 

 CHELIPED.' 



LEON J. COLE. 

 University of Wisconsin. 



While visiting the United States Fish Hatchery at Gloucester, 

 Mass., during the summer of 1908, my attention was called to 

 an abnormal lobster {Homarus americanus) which was at that 

 time preserved in formalin. The specimen was taken in Glou- 

 cester harbor by a local fisherman in the preceding May, and was 

 kept alive in an aquarium at the hatchery about a week before it 

 died. Through the kindness of Mr. Corliss, superintendent of the 

 hatchery, I was enabled to secure the specimen for description. 

 The abnormality consists of a double extra claw on the left cheli- 

 ped, and while not different in general type from specimens which 

 have previously been described, it does possess certain peculiari- 

 ties which would appear to justify placing it on record. The 

 right cheliped was missing when the lobster was caught. From 

 the appearance of the scar, and the fact that there is no evidence 

 of regeneration having begun, it is probable that the loss of the 

 appendage was comparatively recent. The especial interest of 

 the present specimen lies in the fact that the extra claws are so 

 well developed and that their arrangement is almost schematic 

 of the principles, or "rules" of secondary symmetry laid down by 

 Bateson (1894, p. 479), if we make allowance for the torsion 

 which normally occurs in the cheliped of the lobster. 



Description. 



The lobster possessing this abnormality is a male, 237 mm. in 

 length from tip of rostrum to end of telson. 



Claws. — The part which represents the primary claw {PrL 

 of figures) is practically a normal left chela of the crushing 

 type, except for an abnormal outgrowth from its outer (morpho- 



^ Paper from the Zoological Laboratory, Sheffield Scientific School of Yale 

 University. 



252 



