INTERNAL STRUCTURE. 71 



ventriculus, regularly cylindrical and abruptl}^ constricted 

 posteriori}', where it joins the intestine. Twined around the 

 ventriculus are great numbers of small white tubes, the 

 malphighian tubes [mt), which open into the ventriculus 

 where it joins the proventriculus. The ileum (il), or small 

 intestine, is a delicate, light-colored tube, which originates at 

 the posterior end of the ventriculus, and bends abruptly up- 

 ^Yards toward the dorsal surface, where it abruptly en- 

 larges to form the colon (c7), a small, white, sacculated 

 pouch, which lies directly below the terga of the ninth and 

 tenth segments. From this a very short, narrow, rectum 

 runs backward to the anus, which is situated between the 

 podical plates on the lower surface of the eleventh tergum. 



The Reproductive Organs.— The ovary is a long, 

 white gland, situated above the ventriculus and proventricu- 

 lus; it is made up of two sets of tubes or ovarioles, which 

 are bound together into a compact mass. When this mass 

 is carefully examined with a lens the two sets of tubes 

 will be seen to run upwards, forwards and tow^ards the 

 median line. Near the posterior end of the ovary these 

 tubes communicate with two delicate, transparent, ovi- 

 ducts, which run down around the posterior end of the ven- 

 triculus, to the ventral surface of the body. Here they 

 unite to form a single median tube, the vagina, which opens 

 externally upon the upper surface of the subgenital plate. 

 On the median line between the internal plates of the ovi- 

 positor, there is a second much smaller external orifice, 

 which opens into a small white pouch, the spermatheca, 

 which lies above the posterior end of the vagina. 



The Nervous System. — On each arch of the ingluvies is 

 found a small, white, stellate spot, the gastric ganglion, 

 radiating from which are a number of small nerves and a 

 larger commissure, which may be traced forewards into the 

 head, where it joins the supra-oesophageal ganglia, (Fig. 40, 

 oG), which are situated between the eyes, in the upper sur- 

 face of the oesophagus. From them a pair of short commis- 



