
1891.] Embryology 759 
only able to twist their bodies slowly from side to side, as they cling 
to the jelly-mass by means of the suckers below the mouth 
The young tadpoles of the wood frog leave the water as small frogs 
in the late spring of the same year in which they were laid,—that is, 
become frogs in four to six months. Eggs collected about March 
17th began to change to frogs about June rst to 14th. These were 
kept in quite cool water, in a basement room, away from the sunlight. 
At the time of, transformation into tadpoles a sudden decrease in the 
length of the intestine is brought about. The tadpoles cease to eat, 
and the intestine is entirely freed from extraneous matter during this 
time. The change takes place at the same time that the tail is absorbed 
within the body (not dropped off, as popularly supposed), and at the 
same time the pair of fore feet, which were enclosed within the bran- 
chial fold, break through to the exterior. The intestines were removed 
and measured from the pyloric end of the stomach to the proximal end 
of the rectum. Their lengths are recorded in the accompanying 
table for the wood frog : 
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a b c d e J g 
(a) From a large tadpole, with whole tail and two large posterior feet. 
(b) From a tadpole, with whole tail and two large posterior feet. (¢) From 
a tadpole, with whole tail and two large posterior feet. (ď) From a young 
frog, tail beginning to disappear, and four feet. (¢) From a young frog, 
4 tail and four feet. (/) From a young frog, % tail and four feet. 
(g) From a young frog, no tail, and out of water two weeks. 

9. Methods of Technique.-—The eggs during the periods, in which 
it is difficult or impossible to remove the inner jelly membrane, can 
