Intestinal Epithelium of Bufo Lentiginosus. 275 



during the period between the appearance of the posterior and the 

 anterior limbs and takes place in a relatively short time. According 

 to Reuter 48 hours is the maximum time for contraction in Alytes 

 obstetricans. 



Bufo, at a stage corresponding to No. I (Fig. 2), often has a mid- 

 ventral longitudinal strip of the body v^^all which is free from pig- 

 ment. Beneath this unpigmented area the normal peristaltic move- 

 ment of the intestine can be clearly seen. The food is pushed toward 

 the anus by the typical slow, rhythmic, wavelikc contraction. Older 

 larvae, in which the whole ventral surface was deeply pigmented, were 

 etherized, a longitudinal cut was made in the ventral body-wall, and 

 they were then placed in normal salt solution. The normal successive 

 contraction and expansion was obser^^ed as before. Many series of 

 tadpoles, corresponding to the different stages represented in Fig. 

 2, were examined by means of this method. 



Among one lot of especially large strong tadpoles, two individuals 

 were found whose whole bodies remained abnormally free from pig- 

 ment throughout their development. The intestinal movement could 

 thus be observed without opening the body cavity. These two tad- 

 poles were etherized and observed daily until the end of meta- 

 morphosis, one individual for a week, the other for twelve days. 



In no case was anything like a "permanent peristalsis" observed. 

 The records obtained from the unpigmented individuals show that 

 the contraction of the coil is a slow process, extending over the week 

 or ten days previous to the appearance of the fore legs. I should 

 say that X-ray photogi'aphs of the same individual on successive days 

 also prove this to be true. 



From observation of gross conditions, the shortening and narrow- 

 ing of the intestine in Bufo would appear to be accomplished by a 

 very gradual, even contraction of all the muscles, longitudinal and 

 circular, of the intestinal wall. 



Bataillon ('91) ascertained by the measurement of dissociated 

 muscle fibres, that their contraction corresponds exactly to the total 

 shortening of the intestine. 



Although individual variation occurs, this slow contraction of the 

 coil has, as a rule, been completed at the end of the first day after 



