178 THE MICROSCOPE. Dec. 



are formed by invaginatiou frooi without, and are lined 

 with chitin. The mid intestine is the primitive aliment- 

 ary canal. 



The fore intestine is called the stomodaeum, a mouth. 

 It consists (1) of a buccal cavity, from the posterior wall 

 and side of which arises (2) the lingua or tongue (fig. 6, 

 a): a large lobe lying on the median cleft in the labiam; 

 (3) the sBsophagus shown at fig. 5, t; (4) the thin-walled 

 crop (figs. 6, e and 7, e); (5) the thick-walled gizzard or 

 proventriculus, meaning front little stomach (figs. 6, b 

 and 7, b). This has six articular teeth and six elevations 

 carrying setae, on its inner surface. 



The mid-intestine or mesenteron consists only of the 

 true digestive chylific stomach (figs. 6, c and 7, c). 



The hind-intestine is called proctodseum. It consists 

 (I) of a short or narrow intestine (figs. 6, d and 7, d) 

 sometimes called the ileum, (2) a larger or wide intestine 

 (figs, 6, fand 7, f) called the colon; (3) a terminal straight 

 portion or rectum (fig. 6, g). 



The median ventral posterior anus (fig. 7, m) is to be 

 seen by raising the terga of the tenth or last abdominal 

 somite with a forceps. Right and left of it are two 

 small plates, the podical plates. 



Fig. 6 shows the median, dorsal, chambered heart. 



There are ten pairs of stigmata, spiracles, or breath- 

 ing openings: — No. 1, at the bases of the first legs or be- 

 tween the prothorax and the mesothorax; No. 2, at the 

 bases of the second legs or between the mesothorax and 

 the metathorax; No. 3-10 between the terga and sterna 

 of the first eight abdominal somites. The two thoracic 

 and first abdominal stigmata can be seen by raising the 

 wings. The other abdominal stigmata can be seen on. 

 looking at the ventral surface of the animal and stretch- 

 ing it slightly. Each stigma is at the apex of a little 

 projection pointing backwards. The trachesB, in struc- 

 ture, distribution, and functions are like those of the 



