ioo Descriptive Zoology. 



head the segments are all alike. On each side of every 

 segment are muscular projections, called parapodia ; each 

 parapodium has several lobes, and these lobes are provided 

 with bundles of bristles, capable of extension and retrac- 

 tion, and also of being turned in different directions, as in 

 the case of the bristles of the earthworm. By means of 

 the parapodia and bristles the sandworm can crawl, and it 

 also swims by the same means. In the middle region of 

 the body the parapodia serve as gills, and the blood flowing 

 in the thin projections gives them a red color. 



The internal structure, in the main, is very much like 

 that of the earthworm. The pharynx is muscular, and is 

 everted in seizing food ; but the sandworm has a pair of 

 strong, hard, horny teeth, with which it can grasp and kill 

 other worms and small animals that it eats. It also con- 

 sumes vegetable food. It is itself a favorite morsel for 

 many kinds of fish, and hence is much used by fishermen 

 as bait. 



The Leech. Leeches are usually flattened. They have no spines 

 nor appendages of any sort. There are from one to five pairs of eyes 

 on the anterior segments. The body appears to have many segments, 

 but dissection shows that many of these grooves are mere external 

 wrinkles, there being but one partition for from three to five of the con- 

 strictions. There is always a sucker at the posterior end, and in some 

 leeches one at the anterior end also, as in the well-known medical leech 

 of Europe, formerly much used in bloodletting. The mouth has three 

 radiating jaws, each bearing many fine teeth on its edge. The jaws are 

 acted on by muscles which work them back and forth like a semicir- 

 cular saw. The blood thus obtained is sucked into a crop, which 

 makes up the principal part of the digestive tube. The crop has several 

 pairs of side pouches in which the blood is stored, and it is said that the 

 leech can take enough at one meal to last a year. The blood does not 

 coagulate in the crop, and this is said to be due to the action of the 

 saliva. Digestion is accomplished in the narrow stomach posterior to- 

 the crop. A short intestine succeeds the stomach. Leeches have three 



