52 Practical Zoology. 



are sometimes called " hearts." In a recently killed specimen 

 they may be seen pulsating. 



8. In the first six segments is a wide portion of the digestive 

 tube, the pharynx. It has threads of muscle connecting it with 

 the body wall. The pharynx is used as a proboscis, being pro- 

 truded from the mouth and everted. 



9. The pharynx narrows behind into the gullet. This extends 

 through several segments, but is hidden by the sperm sacs and the 

 aortic arches. Clear these away. 



10. In removing the sperm sacs there may be seen in the ninth 

 and tenth segments two pairs of small, white, spherical bodies, the 

 sperm receptacles. The still smaller ovaries may be found in the 

 thirteenth segment. 



11. Back of the spermaries are two enlargements of the diges- 

 tive tube. The first is the crop and the second the gizzard. 



12. From the gizzard to the posterior end of the body extends 

 the intestine. Is it uniform in diameter? If not, where is it 

 wider and where narrower? 



13. Cautiously dissect away the intestine. Under it is the 

 ventral blood tube. From it as well as from the other principal 

 blood tubes there are smaller branches to supply all the tissues. 



14. On the very floor of the body cavity, in the middle line, is 

 the nerve cord, resembling a white thread. Trace it from behind 

 forward. In each segment is an enlargement, or ganglion. From 

 the ganglions proceed branches to supply the surrounding organs 

 with nerve fibers. 



15. Under the anterior end of the pharynx the nerve cord 

 separates into two parts, one passing up on each side to enlarge 

 into a ganglion. These two ganglions are the cerebral ganglions, 

 or brain, and the ring of nerve cord around the pharynx is the 

 nerve ring or nerve collar. 



1 6. Attached to the ventral body wall, on each side of the 

 digestive tube, are many small, threadlike, coiled bodies. Exami- 

 nation with a lens shows a pair of these in each segment. They 

 are the kidneys or nephridia. Each is a tube thrown into loops. 



