INVERTEBRATE ZOOLOGY. 123 



3. The intestinal rosette. This is a set of dilated tracheae belonging to the 

 last three spiracles. It rests upon the dorsal side of the intestine and may be 

 seen by parting the ovaries and removing the overlying fat. It sends branches 

 to supply the rectum and the muscles of the rhabdites. 



4. Dorsal intestinal vessels. These are two of the four main tubes which 

 run longitudinally through the body. They lie ui^on the alimentary canal and 

 extend from the intestinal rosette to the gastric diverticula. They are seen 

 by parting the ovarial or spermatic tubules and reflecting these masses 

 towards the sides. The intestinal vessels are often dilated in places and send 

 up branches to the ovaries or testes, which lie upon them. This supply in the 

 case of individuals -w-ith rijie ovaries, is exceedingly complicated and beau- 

 tiful. 



5. Supply to the gastric diverticula. The arrangement here is very regu- 

 lar and is as follows : The six intervals between the six diverticula are so 

 arranged that two are dorsal (one median dorsal diverticulum Ij'ing between 

 them), two are lateral and two are ventral. The dorsal intestinal vessels send 

 out lateral branches, which, making six with the two ventral intestinal tu- 

 bules, occupy the six intervals ; the main dorsal intestinal vessels occupjdng 

 the two dorsal intervals, the two ventral intestinal vessels, the two ventral ; 

 and the two lateral branches from the dorsal intestinal vessels the two lateral. 

 Each of these six tubules divides anteriorly, the two branches supplying the 

 adjacent sides of the tAvo anterior tubules bordering the intervals. Posteriorly 

 branches from the six tubiiles supply adjacent sides of the posterior diverti- 

 cula. 



6. Supply to the crop. This is the uiost distinct because here the silvery- 

 white tubes lie upon a black back-ground. Four branches, two dorsal and 

 two ventral, extend from the neck-region i)ostei'iorly and meet four which ex- 

 tend anteriorly. The opposing branches anastomose and siipply the walls of 

 the crop with a fine capillary net-work. 



7. The .spiraeula)- tracheae. These are the tubules which come directly 

 from the sx)iracles. From each spiracle come two, dorsal and ventral, which 

 empty into their respective longitudinal intestinal vessel. 



8. Thorax and head. The thorax is richly supplied with tracheal tubes, 

 but these lie interwoven among the muscle fibres and are difficult of demon- 

 stration. From the thoracic system two large tubes, the cephcdic. pass ante- 

 riorly through the neck into the head. The terminal branches of these are 

 provided with verj' numerous small air-sacs. Of these, fifty-three were 

 counted in one specimen. 



