No. 2.] LIMB-MUSCLES [N AMPHIBIA. 131 
in front of the limb and often does not come into contact with 
it. Even when the regenerating abdominal muscle does come 
in contact with the limb-rudiment it touches the limb only at 
its extreme anterior limit, and does not extend throughout the 
limb-region, as it does in normal embryos. Moreover, the limb 
on the side of the injured myotomes always keeps pace in 
development with the limb on the normal side, even from the 
beginning, its growth being wholly independent of whether the 
regenerating muscle reaches the level of the limb or not. 
The constant presence of normal limbs in the injured embryos 
and the fact that in normal embryos there is no local budding 
or proliferation of cells from the myotomes or from the abdomi- 
nal muscle in the posterior limb-region show pretty conclu- 
sively that the limbs in the amphibia are of somatopleuric 
origin. 
General Conclusions. 
The ventral processes from the myotomes in the Urodela 
(Amblystoma and Triton), and in the Anura (Rana and Bufo), 
go to form the ventral muscles of the body-wall. They do not 
go into the limbs as “ muscle-buds,”’ but pass to the median 
side of the limb-rudiments. In the Urodela the pronephros 
develops in the region of the anterior limb. As the pronephric 
tubules elongate at right angles to the direction of growth of 
the ventral myotome-processes, the pronephros pushes the 
myotome-processes over against the limb. The proximity of 
the two structures is a coincidence, and there is no fusion 
between the myotome-processes and the anterior limbs in the 
Urodela. There are no “muscle-buds” in the amphibia such 
as are found in the elasmobranchs and teleosts. In the poste- 
rior limb-region there is no local proliferation from the 
myotomes to the limbs. 
The anterior and posterior limbs in the Urodela and Anura 
arise as thickenings in the somatopleure. The thickening is 
formed zz sztw by the multiplication of mesenchyme-like cells, 
some of which owe their origin to the division of the endothelial 
cells. The myotome-processes as such take no part in the 
formation of the limbs. These results obtained from the study 
