INTERNAL ANATOMY OF THE LOCUST. 263 



of about 15 tubes, so that there are about 150 tubes in all ; at their inser- 

 tion the tubes radiate from the center, and there is a well-marked space 

 on the circumference of the canal between the groups of the tubes. • These 

 vessels are very long ; when stretched out about as long as the body, but 

 are usually much convoluted and wound around the alimentary canal, a 

 few reaching as far as the head. These are excretory organs, and cor- 

 respond to the kidneys of the vertebrate animals. The terminal por- 

 tions of a few only of these tubes are represented in Fig. 14.^^ 



The intestine (ileum) lies in the fifth and sixth abdominal segments ; 

 it gradually diminishes in thickness, and while the surface of the chyle- 

 stomach is smooth, with fine longitudinal muscular fibers, the surface of 

 the intestine has about 12 or 15 large longitudinal ridges, with a few 

 smaller ones. 



Behind the intestines is the colon, which is smaller than the intestine 

 proper, and makes a partial twist. Its surface is smooth. The colon sud- 

 denly expands into the rectum, with G large rectal glands on the outside, 

 held in place by 6 muscular bands attached anteriorly to the hinder end 

 of the colon. In cross-section through the middle of the mass of glands 

 they are seen to be hollow, their cavities independent of that of the rec- 

 tum, though there is an intimate communication between the two. The 

 nature of these glands is unknown. They are lined with epithelial cells 

 and are secretory in their function, and, as Ohun observes, they probably 

 compensate for the want of epithelial secretory cells in the lining of the 

 rectum. The rectum turns up toward its end, and the anus is situated 

 just below the supra-anal plate in the male, while in the female it is 

 placed between the supra-anal plate and the upper pair of spines of the 

 ovipositor. 



In closing our account of the digestive canal, we should briefly describe 

 the salivary glands (Fig. 14, sal.) These are rather difficult to find, as 

 they lie on* the floor of the thorax and are partly covered by muscles and 

 various tissues. The two ducts may be found passing back from under 

 the infra-oesophageal ganglion, and pass straight backward, ending just 

 in front of the insertion of the third pair of legs, and dividing into.no 

 large branches. A -small lateral twig with scattered follicles lies in the 

 prothorax on the outside of the main duct. Behind this is a second mass 

 of follicles like a bunch of grapes attached to two small twigs, one on 

 ' each side. There is a third large assemblage of follicles lying on each 

 side of the second thoracic ganglion, under the metascutum. The two 

 main ducts, according to Mr. Burgess's observations, as seen in his 

 drawing (Fig. 14), unite just before opening into the base of the mouth 

 near the tongue. Our observations were made on Caloptenus femur- 

 ruhrum, as were those of Mr. Burgess. The salivary glands are much 

 simpler and smaller in the locusts than in any other family of Orfehop- 

 tera. 



*2 W'e are inde'bted to Mr. E. Burgess, of Boston, Mass., for tte drawing of Fig. 14, made expressly 

 for, and free of expense to, the Commission. 



