﻿IV. 



Internal Anatomy of Corydalus cornutus in its three Stages of Existence. 



By JOSEPH LEIDY, M. D. 

 {With Two Plates.) 



{Communicated to the Academy, November 8th, 1848.) 



I. Of the Digestive Apparatus. 



1. In the Larva. — The insect, being predaceous in habit, has a structure of the 

 digestive apparatus in accordance with the nature of its food. 



The alimentary canal is a little longer than the animal, in consequence of a single 

 short convolution of the small intestine. 



The mouth opens in an infundibuliform manner into a wide oesophagus, which latter 

 extends backwards through the pro- and meso-thorax, gradually dilates, and forms between 

 the meso- and meta-thorax the proventriculus. 



The oesophagus is thick and strong, and presents distinctly to view three tunics: the 

 external, a delicate, transparent, filamentous lamina ; the central, a muscular lamina, com- 

 posed principally of transverse fibres ; and the internal, or mucous layer, which is thrown 

 into six plicated, more or less regular longitudinal folds, extending its whole length. 



The proventriculus is a strong gizzard, ovate in form, and gradually contracted at its 

 posterior part, forming a tube narrower than the oesophagus which passes back into the 

 abdominal cavity. It is only separated from the oesophagus by a change in structure. 

 Its thickness generally is not greater than that of the oesophagus, but is strengthened by 

 stout muscular columns, projecting in its length from the inner surface of the cavity. 

 These columns are twelve in number, and are exceedingly regular in regard to position 

 and form. Six of them are broad, and alternate with the other six, which are compara- 

 tively narrow. They may be considered as denning the cavity of the proventriculus. 

 The broader columns are on a line with, and correspond to, the oesophageal folds. Each 

 of them consists of two portions : an upper pyramidal, and a lower tile-like or flat por- 



