278 



ARTHROPODS. 



(2) The mid-gut (mesenteron) is lined by endoderm. It 

 is short and narrow, and with its anterior end seven or eight 

 club-shaped digestive outgrowths ("hepatic" c^ca) are 

 connected. These seem to have a pancreatic function. 



(3) The hind-gut (proctodaeum) is lined by a chitinous 

 cuticle. It is convoluted and divided into narrow ileum, 

 wider colon, and dilated rectum with six internal ridges. 

 From the beginning of the ileum, the excretory Malpighian 

 tubules are given oif. 



Respiratory System, — The tracheal tubes, which have ten 

 pairs of lateral apertures or stigmata, ramify throughout the 

 body. 



Circulatory ^System. — The chambered heart lies along the 

 mid dorsal line of abdomen and thorax. It receives blood 

 by lateral valvular apertures from the surrounding pericardial 

 space, and drives it forwards by a slender aorta. The blood 

 circulates, however, within ill-defined spaces in the body. 



The Excretory System consists of sixty or so fine (Mal- 

 pighian) tubules, which rise in six bundles from the beginning 

 of the ileum, and twine through the " fatty body " and in 

 the abdominal cavity. 



Reproductive System 



Of the Male. 



Of the Female. 



The testes are paired organs, surrounded 

 by the fatty-body below the 5th and 

 6th abdominal terga. They atrophy 

 in the adult. 



From the testes, two narrow ducts or vasa 

 deferentia lead to two seminal 

 vesicles. 



These seminal vesicles (the "mushroom- 

 shaped gland ") open into the top of 

 _ the ejaculatory duct. 



This duct opens on the loth sternum. 

 Beside the aperture there are copu- 

 latory structures (gonapophyses). 

 With the ejaculatory duct a gland 

 is associatecl. 



The ovaries are paired organs, in the 

 posterior abdominal region, each con- 

 sisting of eight ovarian tubes. These 

 are bead-like strings of ova at various 

 stages of ripeness. 



From_ the ovarian tubes of each side, 

 ei^ht eggs pass into a short wide 

 oviduct. 



The two oviducts unite and open in a 

 median aperture between the 8th and 

 gth abdominal sterna. Beside the 

 aperture are hard structures (gona- 

 popjhyses) which help in the egg- 

 laying. Here also a pair of " colle- 

 terial ' glands pour out their cement- 

 ing secretion by two apertures. The 

 spermatheca is a paired sac with a 

 smgle aperture on the 9th abdominal 

 sternum. 



