nae BYRNES. [VoL. XIV. 
Sections of an embryo killed four days after injury show that 
the myotomes have not been very greatly reduced, although the 
extreme ventral edges, together with the abdominal muscle- 
rudiment, have been destroyed. The somatopleuric thicken- 
ings of the limbs are equally developed on both sides of 
the body. 
Pl. XI, Figs. 19 and 20, represent sections taken through the 
posterior and anterior parts of the posterior limbs, respectively, 
of an embryo killed four days after injury. Fig. 19 shows the 
primary abdominal muscle on the normal side of the embryo, 
still in contact with the myotome. In Fig. 20 the primary 
abdominal muscle has become constricted off from the myotome 
on the normal side, and is approaching the extreme anterior 
limit of the limb-rudiment. There is as yet no evidence of 
regeneration of the abdominal muscle on the part of the injured 
myotomes on the right side. ; 
An embryo killed seven days after injury shows that the 
myotomes of the posterior limb-region have been reduced to 
one-third their normal length. Notwithstanding the injury to 
the myotomes, the abdominal muscle has begun to regenerate. 
Evidence of this regeneration is seen in the general tendency 
of the mesenchyme-like cells between the myotomes and the 
limb to elongate dorso-ventrally, and to fall into line along 
the path of the developing abdominal muscle. The right limb, 
though slightly smaller than the left, is well developed. The 
difference in the size of the two limbs in this embryo is due to 
the fact that the somatopleure, as well as the myotomes, has 
been injured. This is evident from the abnormal arrangement 
of the blood vessels on the side of the injury. Another embryo 
killed seven days after injury shows the right myotomes greatly 
reduced throughout the whole extent of the limb-region. On 
the side of the injury the abdominal muscle is beginning to 
regenerate. Both the posterior limb-rudiments are present and 
normal. Still another embryo killed seven days after injury 
shows the ventral halves of the myotomes in the right posterior 
limb-region completely destroyed. Near the limb the right 
abdominal muscle has begun to regenerate. Both the limb- 
rudiments appear normal. 
