266 Mary A. Bowers. 



passive crowding of this anterior portion to the right side by the 

 rapid differentiation of the large coil from the posterior yolk mass. 

 This conchision seems justified from experimental work, which will 

 be described later. 



When the coil has reached its maximum length, the liver, lying 

 anteriorly on the right, is very small, but it increases rapidly in size. 

 This growth of the liver on the right, plus a decrease in size of the 

 intestinal coil on the left, and a slight growth in length of the 

 stomach, probably combine to effect the interchange in position of 

 stomach and coil. This is clearly represented in the X-ray series. 

 Figs. 3 to 10. In the twenty-four hours immediately following 

 the breaking through of the fore legs, the shortening of the coil is 

 usually completed (Figs. Y-9) and stomach and coil pass each other 

 in the median line (Fig. 9). At the time the tail begins to shorten 

 (usually on the second day), the change has as a rule been made 

 (there is some individual variation), and the stomach has taken the 

 adult positon on the left side, the reduced coil lies on the right (Fig. 

 10). This transformation of the intestine is described by Eeuter 

 and Duesberg as occurring in Alytes obstetricans and Eana fusca 

 hefore the breaking through of the fore legs. Renter says the 

 rectum changes position slightly or not at all in Alytes. In Bufo 

 it follows the coil from the left to the right side, or, in some cases, 

 only to the median line. It becomes shortened and widened. Besides 

 the shortening of the small intestine, there is also a marked diminu- 

 tion in the diameter,— compare Fig. 18 (before reduction of coil), 

 and Fig. 20 (after reduction), noting the increase in thickness of 

 the circular and longitudinal muscle layers. 



In striving to get a full bismuth-X-ray series, extending through 

 this critical change of shortening and narrowing, it was incidentally 

 determined at exactly what time the larvae stop feeding in prepara- 

 tion for the renewal of the intestinal epithelium. Figs. 11 to 13 

 indicate that feeding continues to the day before the appearance of the 

 fore legs. At the time when the fore legs break through. X-ray plates 

 of many different series show that the bismuth has been eliminated 

 from the rectum (except in a few cases, as Fig. 14). Although the 

 normal food seems to be not so freely eliminated as the bismuth. 



