NOs, 23) LIMB-MUSCLES IN AMPHIBIA. I25 
nevertheless, normal. The right limb is evidently entirely 
separated from the myotome or any of its derivatives; but it is, 
notwithstanding its isolation, in every way comparable with the 
limb on the uninjured (left) side of the embryo. The abdominal 
muscle has regenerated, but only in front of the limb. 
An embryo that had been injured on the 4th of April and 
killed on the 6th of May (thirty-two days after injury) shows 
but little trace of injury to the myotomes. The right myo- 
tomes are slightly shortened, but the relative distances between 
the myotomes and the limbs on the right and left sides of the 
body are about the same and normal. A reconstruction of the 
embryo shows, however, that, whzle the primary abdominal mus- 
cle ts present throughout the whole extent of the limb-region on 
the normal (left) side, on the injured (right) side the muscle ts 
present only at the anterior limit of the limb, and even there tt 
zs veduced to nearly half its normal size. The limbs are well 
developed and seemingly normal; they are, moreover, equal in 
size, and in both limbs the cells that will give rise to muscles 
are already clearly distinguishable from those that will form 
the cartilage. As yet, however, the muscle-fibrils have not 
appeared in either of the rudimentary limbs. Pl. XII, Figs. 
46 and 47, show corresponding sections through the right and 
left limbs of this embryo. 
Sections of an embryo killed thirty-three days after injury show 
that the myotomes have been greatly reduced. The abdominal 
muscle-rudiment comes in contact with the limb only at its 
extreme anterior limit. Both limbs are equally well developed. 
One of the embryos killed thirty-four days after it was 
injured proved to be of particular interest. Pl. XI, Figs. 
29-36, inclusive, show a series of sections taken through the 
limb-region of this embryo. The myotomes are but slightly 
shortened. Throughout the limb-region on the right side of 
the body there is xo indication whatever of the abdominal 
muscle-rudiment. Only at the most anterior limit of the limb 
does the muscle begin to make its appearance (Fig. 36), and 
then it is represented by only a single muscle-cell in which 
fibrils are well developed. Still more anteriorly, in front of 
the limb-region, the right abdominal muscle-rudiment remains 
