No. 2.] EPITHELIUM OF DRAGONFLY NYMPHS. 



at the anterior end and continues posteriorly with the progress 

 of the food. When the nymph has gone long without food 

 and there is much accumulation, the discharge is correspond- 

 ingly great. It is in fact remarkable to see how large a part 

 of the epithelium will thus at once be destroyed. I have 

 chosen, however, to show in the drawings the discharge taking- 

 place after moderate or slight 

 accumulation, as being more 

 normal and on the whole 

 more instructive. 



Fig. 5 represents a normal 

 discharge from epithelium in 

 which the accumulation had 

 been slight and somewhat ir- 

 regular. The portion included 

 between two nidi on the right 

 side is discharged ; that on 

 the left unaffected. The 

 preparation was made from 

 a nymph fed an hour and a 

 half before fixing and from 

 a region just before the mid- 

 dle of the ventriculus. 



Each globule of discharge 

 represents the larger part of 

 an epithelial cell, including 

 generally its nucleus. Sometimes the globule appears to be 

 cut off from the cell substance below it by a wall formed 

 previous to its discharge, but much more often it presents the 

 appearance of having been crowded out by the compression of 

 adjacent cells, in which case it is narrowed to a more or less 

 slender point (B, Fig. 5). In no case have I seen a small por- 

 tion of the cell contents protruding through a cleft in the 

 striated border as found by Van Gehuchten 3 in Ptychoptera 

 contaminata; but in all cases the discharge involved the whole 

 free end of the discharging cell from which the striated border 

 had disappeared as if by solution. 



3 VAN GEHUCHTEN, 1890: Recherches histologiques sur 1'appareil digestif de 

 la larve de la Ptychoptera contaminata, La Cellule, vi. 



B 



FIG. 4. Resting epithelium after two months' 

 fasting, x 220 : parts as in Figs. 2 and 3. 



