FORE-GUT OP CORYDALIS CORNUTUS L. 601 



The chromolytic drops are located near the basement membrane, 

 and it is difficult at times to decide whether one is observing a 

 •degenerating nucleus or one that is massing its chromatin pre- 

 paratory to division. But, judging from the position of these 

 deeply staining masses and the work of previous authors, it would 

 seem conclusive that these are actually degenerating nuclei. 

 None of the degenerating nuclei or cellular contents are dis- 

 charged into the lumen but are undoubtedly absorbed by the 

 neighboring cells. In no case have I observed any part of a 

 cell or its contents discharged into the lumen or forced out through 

 the basement membrane. Cephalad or caudad of this region 

 very few degenerating nuclei are found. 



The epithelial cells show decided secretory activity. The 

 nuclei are prominent, chromatic and located near the bases of the 

 cells (fig. 21). The cytoplasm is granular and almost filled with 

 large vacuoles (figs. 13 and 21). At this period also many nuclei 

 in the gizzard region are undergoing mitotic division. The cell 

 preparing to divide becomes large, migrates to the inner surface, 

 retaining only a very narrow connection with the basement mem- 

 brane, and at the same time possessing a well marked cell wall 

 (figs. 27 and 28). Very few mitotic figures are- found either in the 

 anterior oesophageal region or near the oesophageal valve. The 

 epithelium is still thrown into many longitudinal folds which at 

 this stage practically close the lumen. There is also a consider- 

 able reduction in the diameter of the canal. The changes described 

 above are usually found in pupae from two to three days old. 



At a slightly later period further changes may be observed. 

 There is a constant decrease in the size of the intestine and a 

 marked reduction of the longitudinal folds. The epithelial cells 

 are gradually being reduced in size, due to the active secretion of 

 a very large quantity of pupal intima. The vacuolate condition 

 is also being reduced. Many nuclei throughout nearly the entire 

 fore-gut are undergoing division and many are degenerating 

 The cellular contents possess the same characteristic appearance 

 and give the same staining reactions. Here and there the pupal 

 intima is separated from the underlying epithelium (fig. 29) 



