122 LABORATORY MANUAL FOR ELEMENTARY ZOOLOGY 



dorsal line of the abdomen. Look on the underside of the dorsal strip removed 

 from the animal for a long tubular structure with several dilatations. It is 

 often indistinguishable in specimens which have been preserved for a long time. 

 Fan-shaped muscles are attached on either side to each dilatation ; they are called 

 the alary muscles and are supposed to help dilate the heart. The wall of the 

 heart is pierced with ostia, as in the lobster, through which it sucks in blood 

 from the great blood sinus which surrounds it. 



There are no arteries or other blood vessels, but the blood flows out from the 

 anterior open end of the heart into the sinuses. 



c} The reproductive system: This system will be considered first since it is 

 the first system noticeable on looking into the cavity of the abdomen. In the 

 male the testis forms a white mass in the posterior end of the animal dorsal to 

 the intestine. From each side of the ventral surface of this mass a male duct 

 or vas deferens arises and passes posteriorly and ventrally to the end of the 

 abdomen where it forms a coiled mass, located in the seventh and eighth 

 abdominal segments. The lateral walls of these segments should be removed 

 to see these masses. The two vasa deferentia then unite in the ventral median 

 line within the eighth sternum to a single duct which passes into a muscular, 

 mass surrounding the base of the copulatory organ, or penis. Remove the ninth 

 sternum and the subgenital plate and look for these parts. Remove the muscles 

 from the penis and note with a hand lens or microscope the four hard chitinous 

 styles which compose it. 



In the female the two ovaries are situated in the posterior end of the abdomen, 

 one on each side of the digestive tract. Each consists of a number of parallel 

 ovarian tubes, more or less vertical in position, resting, so to speak, in a row upon 

 the oviduct, which arises from their ventral ends. In each ovarian tube is a row 

 of eggs, of which the largest ones, often plainly visible as oval brown bodies, are 

 placed nearest the beginning of the oviduct. The two oviducts pass posteriorly 

 and ventrally and unite in the median ventral line under the intestine to a com- 

 mon duct, the vagina. The vagina opens to the exterior by the female genital 

 opening located at the base of the egg guide. Grasp the egg guide with a forceps 

 and pull it forcibly out of its position between the ventral styles of the ovipositor. 

 At its base note a little cushion which folds over the genital opening and must 

 be pulled back to reveal the latter. Remove the eighth sternum and locate 

 within it the vagina, a broad tube passing to the genital opening. Lift out the 

 vagina and note just above it another tube, the copulatory sac, which receives 

 the sperm of the male in copulation. This opens to the exterior in common with 

 the vagina. Attached to the copulatory sac is a slender duct leading from a 

 small body located just above the point where the two oviducts unite to form 

 the vagina. This body is the cement gland. In laying eggs the grasshopper digs 

 a hole in the ground with the ovipositor; the eggs are then passed out through 



