Noe 2] LIMB-MUSCLES IN AMPHIBIA. A 
It is the ventral myotome-process in the region of the second 
pronephric funnel which H.H. Field has called ‘“Unwirbel- 
knospe,”’ and from which he derives the pronephric capsule and 
the limb-muscles in Amblystoma. Posterior to the region of 
the pronephric funnels, the myotome-processes permanently 
retain their connection with their respective myotomes, and 
pass directly by the inner side of the limb without any appear- 
ance of fusion with it (Pl. X, Figs. 4, 5). 
These relations are even more clearly seen in Triton than in 
Amblystoma, for, while the body of Triton is relatively wider, 
it has a shorter dorso-ventral axis. Hence, as the ventral edges 
of the myotomes are nearly on a level with the anterior limb- 
rudiment, when the ventral myotome-processes are formed, 
instead of pointing toward the limb-rudiment, as in Ambly- 
stoma, the myotome-processes pass directly by its inner side 
(Pl. X, Fig. 11). In both Triton and Amblystoma the inde- 
pendence of the myotome-processes and the anterior limbs 
becomes more marked in older larvae after the limbs have 
begun to project slightly from the sides of the body. 
The yolk can be largely removed from young Amblystoma 
larvae so that whole preparations can be mounted in glycerine 
or balsam and thus be made perfectly transparent. In older 
embryos the myotome-processes are so closely applied to the 
walls of the coelom that it is often difficult to remove the yolk 
without completely tearing away the myotome-processes or 
breaking them. When the myotome-processes are removed, 
the anterior limb-rudiments a/ways remain intact as a uniform 
thickening of the somatopleure in which there is no evidence of 
any structure comparable with muscle-buds as they appear in 
fishes. This tearing away of the myotome-processes without 
disturbing the limb-rudiments seems to indicate an independ- 
ence of the myotome-processes and the limbs. Pl. X, Fig. 17, 
is intended to show these relations in the anterior limb-region 
of a young Amblystoma larva. 
When the ventral myotome-processes (z.¢., the ‘“ primary 
abdominal muscles’’) and the limb-rudiments in the anterior 
part of the body of Amblystoma are well developed, the myo- 
tome-processes and the limbs in the posterior part of the body 
