42 IOWA STUDIES IN NATURAL HISTORY 
or a total reduction of 28.7 per cent. Curve A’E’, fig. 2, illus- 
trates the changes in the total length of the stomach and in- 
testine during the same period. It also shows a rapid rise un- 
til its highest point is reached; then an abrupt decline. It in- 
dicates a reduction in length from an average maximum of 22.3 
to an average minimum of 12.1 em, or a total reduction of 45.8 
per cent. Curve A’F’, fig. 2, illustrates the changes in the 
length of the stomach alone. Like the preceding curve, it 
shows a rapid rise until its highest point is reached; then an 
abrupt decline.- It indicates a reduction in length from an 
average maximum of 31 mm. to an average minimum of 14 mm., 
or a total reduction of 54.8 per cent. Curve A’C’, fig. 1, il- 
lustrates the corresponding changes in the weight of the stom- 
ach and intestine with contents. It is based on the averages 
of the weight determinations multiplied by 5. It indicates a 
reduction from an average maximum of 1.02 to an average min- 
imum of .32 grams, or a total reduction of 68.6 per cent. Curve 
A’D’, fig. 1, illustrates the changes in the weight of the liver 
during the period of metamorphosis. It also is based on the 
averages of the weight determinations multiplied by 5. This 
curve indicates a gradual increase in the weight of the liver 
throughout the period of metamorphosis. The pancreas in the 
larvae of Ambystoma is relatively small and, like the liver, prob- 
ably undergoes no reduction in weight during metamorphosis. 
The curves representing the total body weight and the weight 
of the stomach and intestine in the larvae of Ambystoma 
tigrinum, with contents, reach their highest point at the same 
time. The curve representing the length of the stomach and 
intestine reaches its highest point a little later. | Obviously, the 
larvae of this species cease feeding before the digestive tube has 
attained its maximum length. At this time the stomach and 
intestine are well filled. As the metamorphic changes advance, 
the contents of the digestive tube are gradually eliminated un- 
til the residue of the undigested matter becomes almost negli- 
gible. The major portion of the weight indicated by the high 
point in this curve is made up by the ingested matter. The 
weight indicated by the low point is approximately the weight 
of the stomach and intestine without contents. 
The period of fasting continues until metamorphosis is com- 
