FORE-GUT OF CORYDALIS CORNUTUS L. 603 



as the major part of the fore-gut consists of a smooth cyhndrical 

 tube. Throughout the entire epithehum there is a gradual reduc- 

 tion in the height of the cells and an increase in the diameter of 

 the intestine. From the time of the shedding of the pupal intima 

 till about the ninth day there occurs a constant increase of cells 

 by mitotic division, and degenerating nuclei are found in gradually 

 reducing numbers. With the definitive formation of the imaginal 

 intima one does not find any more dividing or degenerating nuclei. 



Finally, in a pupa ten days old the epithelium appears in practi- 

 cally the same form as in the adult. It is arranged in numerous, 

 small, longitudinal folds throughout the greater part of the 

 oesophagus. In the posterior portion this folding is very marked. 

 It consists of flattened cells with granular cytoplasm and large 

 nuclei. The vacuolate condition, which was so marked in the 

 early stages, has now disappeared. The great reduction in the 

 size of the cells is due both to the secretion of a large quantity of 

 granular substance which lies between the shed pupal and the 

 forming imaginal intima, and to the increase in the diameter of 

 the canal. The cellular walls are very indistinct or lacking. 

 The imaginal intima appears as a narrow, light area and is now 

 well formed. A basement membrane is present throughout the 

 entire pupal period. At this stage no degenerating nuclei or 

 any undergoing division are found. 



Shortly after the loosening of the pupal intima there occurs a 

 slight outpocketing of the walls of the oesophagus a short distance 

 in front of the oesophageal valve. This has been described and 

 figured by Leidy ('48) who designated it the pupal crop and notes 

 its resemblance to the sucking stomach of Lepidoptera. During 

 its formation the epithelial cells in this region undergo rapid and 

 extensive mitotic divisions. The epithelium lining this outpocket- 

 ing is identical with that of the oesophagus. What its function 

 may be is doubtful. It passes over to the imago as a small 

 appendage of the posterior portion of the oesophagus. 



Cell division 



The phenomenon of cell division in the epithelium of the fore- 

 gut is very characteristic. The cell, preparatory to division, 



