Tissues in the Crustacean Limb. 119 
be thrown off autotomously, although under a slight tension, such 
as may be produced by a gentle pull with a small forceps, the chela 
will, however, usually part in the region between the basipodite and 
ischiopodite, 7: e., at the joint which is destined to develop later into 
the breaking joint of the adult animal. 
TV. Earzty Sraces oF THE REGENERATING Lime. 
1. The Readjustment of Injured Tissues.—Fig. 4 represents a 
longitudinal section of the stump of the right chela just after 
autotomy. ‘The valve (v?) has been carried outwards as the result 
of the amputation and now closes the venous channel ve. The ex- 
posed edge of the layer of epithelial cells of the epidermis (@) pro- 
jects slightly above the level of the broken chitin (ch) of the stump. 
Shortly after autotomy the vascular cavities at the distal end of the 
stump become filled with a dense mass of nucleated blood corpuscles 
(Fig. 7, bc). The muscle (Figs. 2 and 5, m), which was torn by 
the operation, degenerates and is not restored again in the later 
regeneration of the limb, a result which might be expected, for it 
will be recalled that normally this muscle degenerates during the 
fifth stage and is absent in the adult lobster. 
A protecting crust of coagulated blood plasma and blood corpus- 
cles soon becomes evident over the exposed surface of the stump. 
This blood clot (Fig. 7, bcl) forms above, or in other words distal to, 
the connective tissue membrane extending across the limb. The 
relation of this blood clot to the connective tissue membrane differs 
somewhat from that described by Reed (’04) as occurring in the 
erayfish, where the “blood cells form a plug at the opening through 
the membrane, and collect in a thick layer just beneath the ectoderm 
cells, which form the proximal layer of the membrane of the breaking 
joint. . . . After a time these blood cells arrange themselves 
in horizontal lines crowded close under the ectoderm cells of the 
membrane.” Reed further states that “in a few hours from the time 
that the leg is thrown off the membrane takes on the appearance of 
dead tissue. . . . The blood cells soon degenerate, and most 
of them are thrown away with the membrane, when this is later cast 
off” (p. 312). In contrast to this, as may be observed in Figs. 4 
