BIONOMICS AND DEVELOPMENT OF LYGOCERUS sP. 113 
short oesophagus opens into the mid-gut, which fills the greater, 
part of the body cavity, and is lined with glandular cells, rather 
wider than deep, with well-marked nuclei. It contains a mass 
of fluid food material, which is churned to and fro by incessant 
muscular contractions of the body, but until just before meta- 
morphosis there is no communication with the hind-gut. Two 
TExtT-Fic. 11. 
Longitudinal section through the Malpighian tube of a larva of 
the fourth instar, showing lumen. x 300. 
large Malpighian tubes extend from the fourth segment, 
ventral to the salivary glands, and run back on either side of the 
mesenteron. They are somewhat dilated at their anterior 
extremities, and in sections show a considerable lumen, sur- 
rounded by large flattened cells with great nuclei, resembling 
those of the salivary glands (fig. 11). In the posterior half of 
the tubes the lumen is very small and the cells are rounded. 
The tubes open into the ampulla of the proctodacum, that is, 
the cup-like anterior end of the hind-gut, which abuts on the 
mid-gut in the eleventh segment (fig. 14). 
The muscular system is well developed, especially the dorsal 
NO, 257 I 
