NATURAI, HISTORY OF AMERICAN LOBSTER. 



271 



even sharper than before and retain their periodic character. The spines of the lock 

 forceps are also noticeably larger for a time at least. Then follows a characteristic 

 process of concentration and fusion in the spines of the future crusher claw (fig. 24, c. s., 

 and fig. 25, d.), which eventually leads to the reduction of their number. The crushing 

 tubercle is thus formed by the fusion of a greater or lesser number of spines, Uke those 

 of the toothed claw in the fourth to sixth stages. 



In the light of this process are to be explained the "transition forms" which Przi- 

 bram found to arise in the course of regeneration of the crusher claw, showing the knobs 

 as fusing masses of teeth. The occurrence of such transitional stages has also been 

 mentioned by Stahr and Kmmel. 



In th» adult cracker claw (pi. xliii, fig. 2 and 3) the propodus bears two large 

 and six or more smaller tubercles. The big proximal tubercle {p (L), fig. 25) repre- 



Figs. 23 and 24. — Serrate margins of claws shown in figures 21 and 22, in regions marked a and b, and corresponding 

 to periods ii-iv. Two perfect periods of eiglit sharp spines appear in the future lock forceps, and interpolations with 

 fusions of teeth (c s) in the future crusher. 



sents mainly the lock spine of the toothed claw, with the addition of lesser elements, 

 while the great distal tubercle (d.) is composed of a fused mass of upward of thirteen 

 spines, embracing the whole of the third and a part of tne second periods. The dactyl 

 of the crusher also possesses two tubercles of greater size, which close over the intervals 

 between the "molars" of the propodus, besides a dozen or more small ones, resulting in 

 each case from the fusion of several spines. There is also a smaU rounded tubercle on 

 this segment at its proximal end and below the serial line. 



The final differentiations established between the great crusher and lock forceps 

 are illustrated by a perfect set of typical claws from a hard-shelled lobster which must 

 have weighed approximately 12 pounds. In all measurements excepting length this 

 crusher greatly exceeds its fellow, being one-third broader, weighing twice as much (in 

 the dry shell), and having more than double the cubic capacity. In animals of adult 

 size the slenderer claw has often a slight advantage in length over the more powerful 



