52 Illinois State Lahoratory of Natural History. 



character of the walls. This region of the canal is the only 

 part that can be considered an cesophagus. The exterior is 

 devoid of muscular bands and the walls are thin and dis- 

 tensible. There is no trace of calciferous glands. The oeso- 

 phagus, if such it can be termed, is ordinarily crowded into a 

 very narrow space and on casual observation may escape notice 

 as a division of the canal. It may be doubled over the next 

 division. 



Within somites 6 and 7 the walls of the canal become 

 greatly thickened by a development of circularly arranged 

 muscle, and form a powerful grinding apparatus, — the gizzard. 

 Exteriorly this region is noticeable from its pearly lustre and 

 unyielding walls. It really consists of two divisions, belong- 

 ing in somites 5 and 6, respectively, but the backward ex- 

 tension of the septa brings the anterior part within 6 and 

 the posterior part within 7. The line of attachment to its 

 wall of the septum between 5 and 6 indicates the line of 

 separation of the two divisions. This separation is narrow 

 but complete, the wall of the intervening region being thin, 

 and lacking the circular muscle fibers. Longitudinal sec- 

 tions of the gizzard show each part to consist of a zone of 

 muscle which is thickest at its middle, and diminishes in thick- 

 ness, somewhat, anteriorly and posteriorly. The anterior divi- 

 sion of the gizzard is the larger; both divisions decrease a trifle 

 in diameter from before backwards. 



The first division of the intestine is the most slender por- 

 tion of the alimentary canal. It is cylindrical, with smooth 

 and rather firm walls, with a gradually increasing development 

 of chloragogue cells from before backwards, the posterior third 

 becoming dark brown in color from the abundance of these 

 cells. It extends from the gizzard to somite 17, terminating 

 after passing through the i)artition between 16 and 17. The 

 epithelial lining of this division of the intestine is closely cor- 

 rugated. 



Within the posterior part of somite 17 the canal at once 

 expands, loses the chloragogue cells, and becomes thin-walled. 

 This forms the beginning of a second division of the intestine, 

 the largest in caliber of all, extending through somites 18 and 

 19 and terminating in somite 20, where begins the third divi- 

 sion. 



