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 
trachee 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. (2) Make a semidiagrammatic drawing represent- 
ing all the parts of the female reproductive tract. 
