270 Mary A. Bowers. 



It is filled with degenerating material. Its nucleus, like those of the 

 columnar cells, shows an early stage of chromatolysis. There is a 

 pale nuclear groundwork, the chromatin is in deeply stained clumps, 

 the membrane is slightly thickened and is beginning to be irregular 

 in outline. The structure marked ch. appears to be a mass of 

 chromatin in an early stage of degeneration (compare Figs. 38 

 to 41, showing later stages of chromatolysis). The chromatin must 

 undergo chemical change, for increasingly large areas fail to take 

 the hsematoxylin. These unstained areas, in a later stage, are filled 

 with small yellow granules, and in a final stage the whole mass has a 

 clear straw color (Delafield and eosin stain). 



Figs. 35 to 37 show the characteristic appearance of the cells at 

 this stage (No. Ill, Fig. 2). There appears to be fragmentation 

 of the nuclei, also a breaking down of cell walls and a clumping to- 

 gether of nuclei (Fig. 37). 



No. V (Fig. 2) has pushed one fore leg through. Feeding has 

 ceased, the muscular contraction is pronounced (see Figs. 19 and 

 42 for cross sections). The cytoplasm has now become vacuolar, and 

 throughout the cells are scattered globules and granules of brown, 

 yellow and black degenerating substance. The nuclei have become 

 more irregular. 



In No. VI, Fig. 2 (both fore legs through, tail not absorbed), con- 

 traction has been completed and the organs of the alimentary tract 

 are in their adult position (Figs, 20 and 43). Degeneration of the 

 old cells is nearly completed, the cell walls have become indistinct, 

 the cilia have disappeared. 



Marcelin ('03) in his tabulation of the histogenetic changes of the 

 intestinal epithelium of Rana esculenta, shows that the disappearance 

 of the cilia occurs at the time when the intestine is at its maximum 

 length, that is, relatively much earlier than in Bufo. He believes that 

 the reason for this disappearance of the cilia is to be found in the 

 fact that their function, the propelling of the food, is now usurped 

 by peristaltic contraction of the muscles, which have grown stronger. 

 In Bufo the cilia remain throughout the larval life, although there 

 is a strong peristaltic movement, even in very young larvae. 



Figs. 16 and 44 (from the posterior end of the small intestine of 



