56 TROCEEDINOS OF THE ACADEMY OF [1881. 



§ 6. The Intestine, — The location and appearance of the intes- 

 tine, is seen in fig. ST), more clearly in fig. .60. The ileum (il) 

 passes from the posterioi- pole of the abdomen, and appears to be 

 united to the colon (col) by a fold which I have ventured to refer 

 to as the ileo-secal valve {il.v). The rectal glands (re.gl) 

 appear upon the colon, and the rectum (?'e), a strongly chitinous 

 and muscuhir structure, terminates in tlie ciHated anus (an). 



Finally, PI. YIII, fig. 58 ^ will show the relative positions of 

 all the organs opening into the cloaca. See Explanation of Plates, 

 fig. 58. 



We may now construct for further illustration the synthetic 

 figure, PI. IX, fig. 61, giving a side view of the entire intestinal 

 canal in situ. This will indicate the normal position of the crop 

 relative to the abdomen and the other alimentary" organs. It will 

 be seen that it occupies a position anterior and superior to these. 

 The natural tendency of the pressure caused b}^ the expansion of 

 the crop, as it fills the abdominal cavit}', would be to force the 

 remainder of the tract backward and downward. In point of fact 

 it is so fourfd. A number of workers, with abdomens in various 

 degrees of distension wei'e examined, and the condition and site 

 of the digestive organs noted. A few outlines of these abdomens 

 are given : 



The series begins with Fig. 63 (PI. IX), where the crop is shown 

 in nearly normal site, and well filled. 



The same condition is indicated at Fig. 66, except that the crop 

 shows marks of having once been quite distended and afterward 

 emptied. 



Fig. 64 shows a worker, whose crop about half fills the abdomen. 

 The gizzard, gfz, is forced downward (ventral J and has the anterior 

 poles of the sepals turned upward (dorsad;. The effect of sub- 

 sequent pressure (should the crop have expanded), in forcing the 

 stomach, etc., backward and downward into the cloacal cavity, 

 can readily be predicted from the figure. 



In Figs. 62 and 65, the abdomens of workers in the semi-rotund 

 state, the distension has advanced a little further so as to push 

 the stomacli in one case (62) as far ns, in the other (65) partly 

 beyond, the fourth segmental plates, compressing the intestine 

 proportionatel3\ 



1 Adapted from Forel, "Der Giftapparat und die Aurddriisen der Amei- 

 sen," Zeitschrlftf. wiss. Zool., Bd. XXX. 



