158 THE VITAL FUNCTIONS. 



is that of the caterpillar; the second, that of the chrysalis; 

 and the third, that of the moth. The whole canal and its 

 appendages, have been separated from their attachments, and 

 spread out so as to display all their parts; and they are de- 

 lineated of the natural size, and in each case, so as to show 

 their comparative dimensions in these three states. In all 

 the figures, A is the oasophagus; B, the stomach; c, the small 

 intestine; D, the caecal portion of the canal; and E, the colon, 

 or large intestine. The hepatic vessels are shown at r; and 

 the gizzard, which is developed only in the moth, at G, Fig. 

 328. 



It will be seen that in the caterpillar, (Fig. 326,) the sto- 

 mach forms by far the most considerable portion of the ali- 

 mentary tube, and that it bears some resemblance in its struc- 

 ture and capacity to the stomachs of the Annelida, already 

 described.* This is followed by a large, but short, and per- 

 fectly straight intestine. These organs in the pupa (Fig. 

 327) have undegone considerable modifications, the whole 

 canal, but more especially the stomach, being contracted both 

 in length and width :f the shortening of the intestine not 

 being in proportion to that of the whole body, obliges it to 

 be folded upon itself for a certain extent. In the moth, 

 Fig. 328,) the contraction of the stomach has proceeded 

 much farther; and an additional cavity, which may be consi- 

 dered as a species of crop or gizzard (G,) is developed: the 

 small intestine takes a great many turns during its course, 

 and a large pouch, or caecum, has been formed at the part 

 where it joins the large intestine. 



The hepatic vessels are exceedingly numerous in the Crus- 

 tacea, occupying a very large space in the general cavity; 

 and they compose by their union an organ of considerable 

 size, which may be regarded as analogous in its functions to 



* See the figures and description of those of the Nais and the Leech, p. 

 102 and 103. 



f Cams states that he found the stomach of a pupa, twelve days after it 

 had assumed that state, scarcely half as long, and only one-sixth as wide as 

 it had been in the caterpillar. 



