A GRASSHOPPER 17 
The male organs. ‘The paired testes which secrete the sperma- 
tozoa lie above the intestine, bound together by connective 
tissue and fat. Each testis consists of a bundle of elongated 
tubes with which a duct called the vas deferens connects poste- 
riorly. The two vasa deferentia run, one on each side of the 
intestine, to the ventral side of the animal, where they meet 
to form a median tube, called the ductus ejaculatorius, which is 
homologous to the vagina of the female. Connecting with 
the ductus ejaculatorius are a number. of tubular prostate 
glands which secrete the fluid in which the spermatozoa are 
suspended. 
Exercise 15. (6) Make a semidiagrammatic drawing representing 
all the parts of the male reproductive tract. 
The respiratory system. The spiracles have already been noted. 
They are the external openings of the trachee, a system of fine 
air-tubes which extend throughout the entire body of the 
insect and through which fresh air is introduced into every 
part of the body. The blood is thus constantly aérated, and 
there is never any venous blood present. This arrangement 
results in a very active metabolism, and is one of the causes of 
the extraordinary amount of energy which characterizes most 
insects. With the aid of a hand lens examine the trachee in 
different parts of the body. They may be easily detected by 
their silvery gleam. Notice the arrangement of the main 
tracheal trunks, including those which connect with the spiracles, 
also the arrangement of the air-sacs, which are expansions of 
traches. Mount a small portion of the fatty tissue containing 
tracheze in water or glycerine and examine them with a com- 
pound microscope. Notice the spiral threads which line the 
trachez. 
Exercise 16. Make a drawing of a trachea seen under a high 
power of the microscope. 
