108 BYRNES. [VoL. XIV. 
Methods. 
Most of the embryos were killed in a saturated solution of 
corrosive sublimate to which five per cent acetic acid had been 
added. The embryos were subsequently sectioned and stained 
on the slide with Delafield’s haematoxylin, followed by a wash 
of picric alcohol. This method, when used on amphibian 
embryos, gives a very sharp differentiation of muscle-fibers, 
staining them a bright yellow color, while the chromatin in the 
nuclei remains a deep purple; the protoplasmic network remains 
faintly stained with the haematoxylin. Other double stains 
were used to detect the presence of muscle-fibrils, but they 
gave no better results than the method already described. 
I. NorMAL DEVELOPMENT OF THE MyoToOME-DERIVATIVES, 
ANTERIOR AND POSTERIOR LIMBS IN THE URODELA (Am- 
BLYSTOMA AND TRITON). 
Since the limb-muscles are derived directly from the myo- 
tomes in some of the lower vertebrates, and a similar process 
is believed to take place in the higher vertebrates, the develop- 
ment of the limb-muscles in higher forms must be studied in 
connection with the fate of the myotome-derivatives. Maurer! 
has already described the formation of myotome-processes in 
Amblystoma (Siredon) and has given a detailed account of their 
subsequent development into the muscles of the body-wall. He 
has not, however, considered the relation of the myotome- 
processes to the limbs. As my attention has been directed 
chiefly to the earlier stages in the formation of myotome-proc- 
esses and to their relation to the limbs, I shall, for the sake of 
completeness, give a brief account of the ventral myotome- 
processes up to the time when they first begin to develop 
muscle-fibrils. 
In Amblystoma all the myotomes of the trunk-region, ex- 
cepting the first and second, give rise to ventral myotome- 
processes which are alike in'structure. The myotome-processes 
develop first in the anterior part of the body, where they appear 
1 Morph. Jahrob., Bd. 18, Heft 2, 1892. 
