370 THE GYPSY MOTH. 



stomach (ps) extends backward from the anterior stomach 

 to the eleventh segment and nearly fills the body cavity. 

 The contents of this organ are of a more solid nature than 

 those of the anterior stomach. In the eleventh segment 

 this organ tapers abruptly to form the short intestine (i) , 

 which has two enlargements, separated from each other by 

 a sharp constriction. Between the stomach and the intes- 

 tine, and also where the intestine enters the rectum, there 

 is a well-marked constriction. In the last body segment 

 the intestine expands into the large distended rectum (r) , 

 which completely fills the cavity and discharges at the anus 

 beneath the anal shield. Six narrow longitudinal muscles 

 extend the entire length of the alimentary canal. These 

 muscles form six definite depressions on the intestine and 

 rectum, and give to the excrement of the larva its peculiar 

 incised appearance. 



The malpighian vessels (Fig. 1 , mv) consist of six double 

 convoluted tubes which are attached to the walls of the pos- 

 terior stomach ,and discharge into the intestine. These ves- 

 sels are simply convoluted tubes (Fig. 9), and do not pos- 

 sess the bulbose lateral enlargements found in many other 

 Lepidoptera. They are composed of a thin outer membrane 

 and an inner layer of thick-walled nucleated cells, arranged 

 around a central lumen, some parts of which, in the alco- 

 holic specimens, are often filled with a yellow-brown crys- 

 talline mass (urates) . Fresh malpighian vessels macerated 

 in water give quantities of minute crystals. I have been 

 able to demonstrate the presence of uric acid in these ves- 

 sels by the use of the " murexid " test. 



Small white granules are occasionally found deposited 

 throughout all the different tissues of the larva, but, owing 

 to their extremely small size, I have been unable to collect 

 a sufficient quantity for analysis. In similar granules re- 

 moved from the tobacco worm (Protoparce celeus) I have 

 found uric acid, as shown by the " murexid" test, and 

 phosphoric acid, as demonstrated by the reaction with am- 

 monium molybdate. 



The silk glands, two in number, lie along the lateral walls 

 of the body cavity of the larva. Each gland consists of a 

 small thread-like tube, which leads forward from the poste- 



