THE AMERICAN LOBSTER. 107 



The power of regenerating a lost part varies in both vertebrates and invertebrates 

 in direct proportion to the physiological importance of the part, as Weisinann has 

 clearly shown, -hist as the enemies of the lizard seize it by its long' trailing- tail, so the 

 lobster is almost invariably caught by a claw, and the life of the animal is often saved 

 in either case by the breaking off of the member. The plane of fracture in the limb, 

 as in the large cheliped of the lobster and in the five pairs of pereiopods of the crab, is 

 a secondary structure which coincides with the plane of articulation of two coalesced 

 joints, yet Leydig has shown, according to Weisinann, that the tail of the lizard is 

 specially adapted for breaking oft, u the bodies of the caudal vertebne from the 

 seventh onward being provided with a special plane of fracture, so that they easily 

 break into two transversely.'" (The Germ-Plasm, p. 116.) The regenerative power 

 is probably a secondary characteristic which has been acquired by natural selection, 

 for the good of the species, while autotoiny is a much more recent acquisition. As 

 Weisinann says, "there is no such thing as a general power of regeneration" among 

 animals as with crystals, but "in each kind of animal this power is graduated according 

 to the need of regeneration in the part under consideration." 



Weismann rejects the idea of a spiritus rector, or external directing agency, and 

 assumes that the nisus formativus is situated in the " idioplasm" of the cell, and "that 

 each cell capable of regeneration contains an accessory idioplasm, consisting of the 

 determinants of the parts which can be regenerated by it in addition to its primary 

 idioplasm." He furthermore infers that the general capacity of all the parts for regen- 

 eration may have been acquired by natural selection in the lower aud simpler forms, 

 and that it is gradually decreased in the course of phylogeny in correspondence with 

 the increase in complexity of organization. 



Weismann attempts, in a very ingenious way, to harmonize the facts of regenera- 

 tion in animal embryos with the " mosaic theory" of development of Eoux, but, as E. B. 

 Wilson (206) remarks, the two fundamental postulates of this hypothesis, "namely, 

 qualitative nuclear division and accessory latent idioplasm, are purely imaginary." 

 The theory of Eoux and Weismann has its counterpart in the view advocated by 

 Whitman (204), that "in the development of the germ, in the repair of injured parts, 

 and in the regeneration of lost parts the organism as a whole controls the formative 

 processes goiug on in each part." 



While no final explanation of the process of regeneration can now be given, and 

 the idea of a formative power is, as Whitman says, one of profound mystery, the 

 solution of which appears to lie as far beyond our grasp to-day as at any time in the 

 past, yet we are in a better position to-day, if not to give answers to these questions, at 

 least to point out the probable direction in which they should be sought. 



1 shall consider the question of regeneration again in connection with the origin 

 and perpetuation of deformities in the lobster. 



INTERNAL CHANGES IN REGENERATION. 



The histogenesis of the new limb is not easy to understand, although it can be 

 followed without much difficulty after the papilla stage. 



I am unable to find any trace of " glandular-like" bodies such as Goodsir described 

 (80) as furnishing germs of the new limb. On the contrary, the new limb appears to 

 arise mainly by growth of the connective tissue cells already present in the stump. 



After the blood has clotted over the wound and has produced a hard crust, the 

 cuticular cells, in response to the stimulus thus received, grow over the wound and 



