262 Annals Entomological Society of America [Vol. XV, 



below the first pair, the second pair arises and extends, each member 

 of the pair upon its respective side of the alimentary canal, forward 

 for the remaining distance of the sixth segment where it turns back- 

 ward and taking an upward and lateral direction, with regard to the 

 intestine, curves and coils about in the lower part of the abdomen back 

 of the sixth segment. The third pair of tubules is situated upon the 

 venter about equidistant from each other and from the corresponding 

 members of the second pair. This third pair extends backward 

 immediately and each member comes to lie beneath and to the side of 

 the intestine, intertwining with the corresponding member of the 

 second pair. The tubules are irregular in outline, appearing like small 

 oval beads strung upon a thread. In general color they are a pale, 

 clear yellow, but blotched at irregular intervals with a kidney-brown 

 pigment. They weave in and out among the fat bodies and tracehae, 

 and into blood sinuses to perform their function of the removal of 

 nitrogenous waste. 



The front end of the intestine is cup-shaped with the larger end 

 forward. This portion represents the small intestine. The tube 

 grows smaller as it proceeds toward the caudal end. but in the seventh 

 segment is greatly constricted; it enlarges immediately and passes 

 through segment eight with a diameter of about a fourth that of the 

 segment and two-fifths of the diameter of the mesenteron in the first 

 segment. This portion represents the large intestine. 



At the posterior margin of segment eight, the intestine is again 

 constricted and passes over into the rectum. At this juncture there is a 

 semi-valve formed by the invaginated walls of the intestine. These 

 folds become longer and fewer in number and form the blood gills which 

 lie in the rectum. The rectum extends through the ninth segment. 

 In some forms examined, the small diameter of the constricted region 

 at the posterior end of segment seven prevails through the eighth, 

 widening suddenly at the beginning of the ninth to accommodate the 

 invaginations forming the blood gills; in other forms the widening is 

 gradual through the eighth and passes over gradually into the rectum 

 without any noticeable constriction. The wall of the small intestine 

 is heavy and surrounded with circular muscles. It becomes thinner as it 

 extends toward the large intestine. When the rectum is reached the 

 wall is exceedingly thin and almost transparent. Through the wall 

 can be seen the four pockets or invaginations which form the blood gills, 

 and into these muscles extend from the lateral and ventral walls at the 

 conjunctiva between segments. eight and nine. The rectum now serves 

 a double function, that of elimination of fecal matter and secondarily 

 that of respiration, when oxygen cannot be obtained by means of the 

 tracheal gills. These blood gills have no tracheee running into them 

 as a glycerine mount of the caudal portion of a fresh specimen clearly 

 demonstrates. They function, when the larva is out of the water, by 

 protruding themselves through the T-shaped anus, in which state they 

 are filled with blood. A detailed account of their structure will be 

 found elsewhere in this paper. 



