16 INVERTEBRATE ZOOLOGY 



The excretory system. This system consists of the Malpighian 

 tubules. These are delicate tubular glands, about fifty in num- 

 ber, which unite with and discharge their products into the 

 alimentary canal at the point of juncture of the stomach- 

 intestine and the ileum. They extend freely into the body- 

 cavity and excrete urinary wastes from the blood, in which 

 they lie immersed. 



Exercise 14. Make a drawing of the alimentary canal and the 

 Malpighian tubules on a scale of 7 and label all of the 

 parts. 



The reproductive system; the female organs. The two ovaries 

 are closely bound together by a web of connective tissue and 

 tracheae so as to form a single mass, which lies above the 

 intestine. If your specimen be a female, part this mass along 

 the median line and with a needle gently remove some of the 

 connective tissue surrounding it. Examine it with a hand lens ; 

 each side is a separate ovary and will be seen to be a collection 

 of parallel, tapering tubules, their smaller ends being in the 

 median line, their longer ends projecting back to the tube-like 

 oviduct. These tubules are called ovarioles ; it is in them that 

 the eggs develop. How many tubules do you count on each 

 side ? Notice the elongated eggs in each ovariole. How many 

 do you see in each one? The two oviducts proceed from the 

 ovaries to the ventral side of the animal, where they unite to 

 form a median tube, the vagina, which opens to the outside 

 between the ovipositors. Just above the vagina is a small sac, 

 the receptaculum seminis, which is connected by a long sinuous 

 duct with the exterior. This sac becomes filled with sperma- 

 tozoa during pairing, which fertilize the eggs as they pass out 

 of the vagina. 



Exercise 15. (a) Make a semidiagrammatic drawing represent- 

 ing all the parts of the female reproductive tract. 



