IO4 NEEDHAM. [VOL. I. 



longitudinal muscle fibers. Sadones 2 has made careful study 

 of all these parts in the nymph of Libellula depressa L., and 

 they have been studied in other insects by many investi- 

 gators. 



The part of the ventriculus for which all other parts exist is 

 the epithelium, and although this part has received much atten- 

 tion, there is among investigators little concord of opinion as 

 to the meaning of certain of its structures. The purpose of 

 this paper is to record the results of some additional studies of 

 a combined histological and physiological nature upon this part. 

 Grateful acknowledgment is clue Prof. S. H. Gage for kind 

 assistance and advice in the prosecution of these studies. 



The nymphs of dragonflies are favorable subjects for studies 

 of this sort, being everywhere common in fresh water, and 

 easily collected, easily kept, and easily fed. A dish of water 

 with some sand and a few plants in it furnished a congenial 

 home for my nymphs so long as I kept them alive; and larvae 

 of Diptera, or when these failed, bits of live earthworm, served 

 well for food. The species mostly used were Leptetrum quad- 

 rimaculatnm L., which lives sprawling upon the trashy bottoms 

 of ponds, AescJma constricta Say, which clings to submerged 

 vegetation mostly in streams, and GonipJins descriptus Banks, 

 which burrows in the bottom of both streams and ponds. There 

 was found no appreciable difference in structure correlated with 

 their difference of distribution in depth and consequent differ- 

 ence in food; and the species last named was the one used 

 most extensively. It is the one from which the figures have 

 been drawn. 



Methods. - - For the study of the accumulation of the diges- 

 tive secretion, some nymphs were kept until wanted in a bare 

 dish of water, where there was no chance of obtaining food. 

 For the study of the discharge of this secretion other nymphs 

 of the same size were fed at regular intervals for a time to 

 bring them into the same condition, and then killed at different 

 intervals after their last feeding. For general morphology, 

 picro-aceto-sublimate (Rath's) was used for fixing, and was fol- 



2 SADONES, 1895 : L'Appareil digestif et respiratoire larvaire des Odonates, La 

 Cellule, xi. 



