120 BYRNES. [Vor. XIV. 
limb on the side of the injury to keep pace with the limb on 
the uninjured side of the embryo wethout first regenerating 
themselves. 
A few preliminary experiments were made on the tadpoles of 
Rana sylvatica, and these showed that the Anura offer much 
more favorable conditions for the experimental study of the 
limb-tissues than do the Urodela, as has already been stated. 
This is owing to the greater distance between the myotomes 
and the limbs in the Anura,—a condition which makes it 
possible to destroy the myotomes without necessarily involving 
the somatopleure of the limb-region in the injury. 
On the roth of April, 1895, eighty embryos of Rana palus- 
tris (7 mm. to 8 mm. in length) were taken from their 
capsules, and the ventral halves of the myotomes in the 
posterior limb-region were destroyed. On the 11th of April 
similar operations were made on forty more embryos from the 
same set of eggs. In all cases the operation was performed on 
the right side of the body. All these embryos (one hundred 
and twenty in number) survived the operation and were kept 
in the laboratory in an apparently healthy condition for periods 
varying from two days to six weeks. Some of these embryos 
showed the effects of the injury by a very perceptible shorten- 
ing of the dorso-ventral axis of the right side of the body and 
by a bending of the tail sideways through an angle of ninety 
degrees. From the 12th to the 23d of April some of these 
one hundred and twenty tadpoles were killed daily. After that, 
a few were killed at intervals of several days until the 4th of 
June, when all the remaining tadpoles of the set were killed. 
Normal embryos were also preserved as a check to the injured 
series. 
Many of the injured embryos have been disregarded as giving 
inconclusive results. None of the discarded embryos, however, 
furnish any evidence against the somatopleuric origin of the 
limb-muscles. Many of them show only the normal relations, 
in the posterior limb-region, between the myotomes, the abdomi- 
nal muscles, and the limbs. In some of the earlier experiments 
the injury was confined to the extreme posterior part of the 
body. Many embryos, thus injured, were kept for several 
