3 
after decapitation thirteen of the larvae were living. These were 
carefully compared with the controls and no differences were observ- 
able in general growth, but a remarkable change occured in pigmen- 
tation during these 24 hrs. The black chromatophores were contracted 
to one half their normal diameter. These changes in pigmentation 
will be considered later. 
Larvae 17-18 mm. On July 12th, about six days after decapi- 
tation, eleven larvae were still living. Comparing these with the con- 
trols some differences are apparent. Nine of them conform, in general 
contour of body, to the normal larvae, while two show a somewhat 
pronounced ventral curvature of the posterior portion of the body 
and tail. In some of them certain problematic structures are observed 
in the tail which give it a peculiar appearance. These structures 
show as more or less radial striations. This row of striations extends 
along the lower margin of the tail, from the anus to the level of 
the posterior limb. As development progresses they become more 
pronounced. Their significance, however, can be interpreted only 
after a careful study of sections. 
Larvae 19-20 mm. July 18th the normal and the eleven de- 
capitated larvae were again compared. The average length of the 
normal larvae from the anterior margin of the gills to the tip of the 
tail is 17 mm. The decapitated larvae average about 16 mm. The 
average length of the tail in ten normal larvae is 8 mm. as compared 
with 7 mm. in the experiments. The gills show some rather striking 
differences as will be observed when Figs. 2 and 3 are compared. 
The gills in the normal are long and slender while in the decapitated 
they are short and thick. The filaments show but little difference in 
numbers, but in their position are more irregular in the decapitated. 
The anterior limb buds have attained the same degree of differentia- 
tion. In both they show the beginnings of three digits. 
Larvae 24-25 mm. August 8th the normal and decapitated 
larvae were again compared. Nearly all the decapitated at this time 
show a more or less pronounced ventral curvature of the posterior 
portion of the body and tail. In most of the decapitated the yolk 
has been absorbed somewhat slower that in the normal. In two the 
rate of yolk absorption was so much retarded that the larvae died 
from abdominal hernia. The gills and gill filaments show about the 
same differences as in the earlier stages. The limbs have reached the 
same degree of differentiation as in the normal. 
1* 
