88 PROCEEDINGS OF THE ACADEMY OF [March, 



This part of the hind-gut, from about section 1 to section 35, 

 anterior part of segment VII (Fig. 6), seems to be homologous with 

 the ileum or small intestine of the Orthoptera (Minot, 1880, pp. 

 209, 217; Packard, 1898, pp. 316, 317; Bordas, 1898, pp. 48 and 52), 

 and with the small intestine of Anisopterous larvae (Sadones, 1895, 

 pp. 277, 279, 291; Faussek, 1887, p. 708; Tillyard, 1916, p. 131). 

 In his recent book on the Dragonflies (Tillyard, 1917, pp. 101, 113, 

 114) Tillyard calls this division of the hind-gut the short intestine; 

 but there is present here no ventral pad of thick columnar epithelium 

 as described by that author and Sadones. In Fig. 1 of sect. 20, we 

 have from within outward: the chitinous intima, ?"; the epithelial 

 layer, e; the basement membrane, 6; and the circular muscular 

 coat, cm. The cells of the epithelial layer are not all of the same 

 size. The largest are those of the apical portions of the longer 

 folds. Here the cells are elongate and, in the transverse sections 

 of the ileum, appear somewhat wedge-shaped, with the bases of the 

 wedges next the intima. In the shorter folds, and in the furrows 

 between the folds, the cells are much flatter. The basement 

 membrane follows the folds of the epithelium mesad, leaving, as a 

 result, triedral spaces between itself and the circular muscle coat; 

 these spaces are filled with blood. 



Just posterior to section 20 (Fig. 1 and 6, row 4 of slide 1), three 

 (Nos. 4, 8, and 12) of the above six large folds gradually broaden 

 out, become flatter, and transform into the three broad longitudinal 

 bands of thick columnar epithelium seen at section 55 (Fig. 2, row 

 5 of slide 1). The other nine folds, i. 2. 3 — 5. 6. 7 — 3. 10. n, 

 consisting of the epithelium mentioned in the preceding paragraph, 

 are also present at this point. Figure 2 represents the appearance 

 of the hind-gut between sections 35 and 80. It is probably homolo- 

 gous with the prerectal ampulla of some Orthoptera (Bordas, 1898, 

 pp. 52, 48) and of Anisopterous larviB (Sadones, 1895, pp. 280, 295; 

 Tillyard, 1916, Plate 31). Sadones describes two broad bands of 

 thick epithelium separated from one another by folds of a different 

 kind of thin epithelium, in the prerectal ampulla of the larva of 

 LiheUula depressa. Tillyard's description of this section of the gut 

 agrees with that of Sadones (Tillyard, 1917, pp. 101, 113, 114). 

 The diameter of the gut, too, is here greater than in the parts of the 

 digestive tube immediately preceding and following. But both 

 Sadones and Faussek (1887, pp. 708, 709) state that two kinds of 

 epithelia also occur in the ileum of Anisopterous larvse. Faussek, 

 indeed, does not mention the occurrence of a prerectal ampulla in 

 Aeschnid larvse. 



