28o BULLETIN OP THE BUREAU OF FISHERIES. 



The armature of the toothed claw of a seventh-stage lobster and that of the eighth 

 stage from the same individual are given in figures 4 and 5, plate xlii. The formulae for 

 three typical periods in similar stages of another individual are also tabulated (table 5, 

 no. iia and 116). It will be seen that five new spines have been gained in the course 

 of this molt, and that one of them (the second in series iii) belongs to the sixth order, 

 while three have dropped out. 



Similar changes were effected in the course of the molt of an adult lobster (lengths 

 before and after molting, i iX and i2>^ inches, respectively) , and are illustrated in figures 

 26-29, where the spines are represented in profile and in horizontal projection. The 

 "dental formulae" are also given (table 6, no. 12a and 126), from which it appears 

 that five spines have been gained without corresponding loss in the three periods con- 

 sidered. More interesting changes have occurred at the proximal end of the jaw, where 

 five characteristic large spines (a-e, fig. 27 and 29) have been retained, but the inter- 

 mediate smaller groups (/—i) have lost from one to two members in three instances and 

 in one case have gained two. Spine i has moved toward the lock spine, and bears two 

 satellites, which seem to be thrown off as buds. The large tooth of the first order in the 

 proximal period (iv, i) has also received new recruits upon either hand (iii, 4, and iv, 4). 



Looking at the jaw as a whole, it has lost 6 teeth and gained 9, the first period alone 

 having suffered no change in numbers. At the beginning of the molt the jaw was pro- 

 vided with 49 teeth, while at its close it possessed 52. 



This suppression of old and emergence of new teeth probably goes on all the time 

 in the life of this crustacean, but the changes must be compensatory, for no substantial 

 losses or gains in the complete armature are finally registered in animals of great age. 

 It will be observed that new spines often occur in the most crowded places, and it 

 seems probable that such intercalated members arise as buds from their larger neighbor, 

 as suggested above. In the earlier stages, however, there is no evidence of budding 

 growth or division at the surface. As to why in certain parts (groups f-h, fig. 27 

 and 29) teeth are summarily suppressed, we can only hope that at some future time 

 light may be thrown on such obscure questions. 



