FORE-GUT OF CORYDALIS CORNUTUS L. 599 



In the larva not preparing to pupate (fig. 17) the narrow, inner, 

 chitinized layer stains densely black with iron-haematoxylin 

 while the remainder usually shows a very characteristic laminate 

 appearance. In the prepupa, at the time of molting of the larval 

 intima, the black area is much increased and the inner layer loses 

 somewhat of its laminate structure. It has a broken down appear- 

 ance, often reticulate, the loose intertwining strands filling the 

 space between the epithelium and intima (fig. 19). The base- 

 ment membrane is sharply differentiated throughout the entire 

 prepupal period. 



Changes at time of pupation 



The external changes in size, shape, et cetera, may be seen in 

 figure 11. In this pupa the intima of the gizzard was not dis- 

 charged at the molt but remained lodged at the anterior end of 

 the oesophagus. The fore-gut is now a long, cylindrical tube prac- 

 tically empty, while the mid-gut is greatly expanded by a dense, 

 yellowish fluid. None of this fluid extends into the fore-gut 

 except at its posterior end where the nearly evaginated oesopha- 

 geal valve fails to form a closing bridge. A short distance cepha- 

 lad, however, the fore-gut is completely closed. 



As Corydalis larvae, under similar conditions,' vary so much 

 individually in the time spent in the pupal chamber before pupa- 

 tion, as well as the pupae in the time occupied before the emergence 

 of the adult, I have found it impossible to follow the changes 

 according to the time element. The changes to be described here 

 as occurring at the time of pupation cannot be said to always 

 occur at this period, since my experience shows that the indivi- 

 dual larvae pupate when different histological changes are in 

 progress. I shall, therefore, present in as connected and as logi- 

 cal a way as possible the changes that occur throughout pupation 

 up to the time of the emergence of the adult, without special 

 reference to the particular time at which these changes are to be 

 observed. 



With the shedding of the larval intima the oesophageal valve 

 becomes partially evaginated and appears in cross-section as a 



