NATURAL HISTORY OF AMERICAN LOBSTER. 
267 
In the fourth stage the great claws are not only symmetrical, but of the toothed 
type. According to Emmel (96) the transition to the asymmetrical condition begins 
in the sixth stage, but in the material studied as a basis for this account it was impossible 
to detect any morphological differences until the seventh or succeeding stage. There is 
doubtless some variation in this respect. It is true that at preceding periods the big 
claws may differ in size or slightly in form as a consequence of molting or regeneration, 
but without implying the differentiation in question. Again at the seventh stage these 
lock spine; p, compound proximal tubercle of crusher claw. Enlarged about 34 times. 
claws may appear to the naked eye essentially alike in form and size. Thus, to give 
a concrete example, a lobster in the eighth stage, measuring 19.75 milimeters, September 
22, showed a rather striking similarity in the forceps, the dimensions of which were as 
follows : 
Right claw (future crusher): Millimeters. 
Length 7 
Breadth .. 1.7 
Left claw (future toothed forceps): 
Length 7 
Breadth 1. 4 
