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 Weismann has 
clearly shown. Just 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 Weismann, that the tail of the lizard is 
specially adapted for breaking off, “the bodies of the caudal vertebrae 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 autotomy is a much more recent acquisition. As 
Weismann 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 and 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 going 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-dav, 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 uuable to find any trace of “ glandular-like” bodies such as Goodsir described 
{SO) 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 m 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 
