58 THE LARVA OF THE RLOW-FLY. 



large conical cells, of from 20" to 30" in diameter, which are 

 often 80" from base to apex, with large ovoid nuclei. These 

 cells are distinctly striated towards its lumen (PI. I., Fig. 6) ; 

 there is also a layer of sub-epithelial or parietal cells {gc), 

 which are probably glandular, and a large number of very 

 remarkable cell-nests (c «) are scattered between the epithelial 

 and muscular coats. They are formed of small flattened cells, 

 5" to 6" in diameter, arranged in concentric layers. They are 

 most numerous in the chyle stomach, and are found in the 

 proximal intestine. They are absent in the gastric caeca. 

 These curious bodies are apparently the histoblasts from 

 which the mesenteron of the nymph and imago are developed. 



The Proximal Intestine is 9 mm. long (fths of an inch). After 

 making a dorsal flexion forwards {the hcemal flexure), it passes 

 backwards (Fig. 10), and forms several coils in the twelfth 

 segment. It becomes much narrowed, and terminates in the 

 sinus. 



There is a distinct ring of embryonic cells which surrounds 

 the sinus at the orifices of the Malpighian vessel. This 

 Kowalevski regards as the rudiment of the proctodseum of the 

 imago. I consider it the rudiment of the metenteron, which 

 was unknown to Kowalevski. 



The muscular coat of the chyle stomach and proximal intes- 

 tine has the appearance of a lattice-work, with considerable 

 spaces between the fibres ; that of the sinus is very thin. 



The Distal Intestine (PI. I., Fig. i, i') is chiefly coiled up with 

 the proximal intestine and the vessels of Malpighi in the twelfth 

 segment. It measures 18 mm., or Jths of an inch, in length. It 

 is very narrow and has a thick muscular wall, which consists 

 chiefly of circular muscle fibres. Its epithelium has a clear 

 mucoid character, and amoeboid corpuscles are seen within and 

 between the cells (PI. I., Fig. 7, c), which frequently exhibit 

 goblet degeneration. 



The Rectum is not more than i mm. (a'sth of an inch) in length, 

 and descends almost vertically from the dorsal towards the ven- 

 tral aspect of the larva. The epithelium is flat, and is covered 

 internally by a thick longitudinally plicated cuticle. The 



