ADDITIONAL ANIMAL STUDIES 179 



stance within which the animal can withdraw when danger 

 threatens. In the case of the red coral this material is horny. It 

 is used for decoration, and some communities on the Mediterranean 

 are devoted largely to the gathering of this coral, and to making 

 it into various forms of jewelry. 



C. Annelida 



134. Earthworm. The most common representative of the 

 annelida is the earthworm (Fig. 128). The general form of this ani- 

 mal is long and cylindrical. If one places an eartftsvorm on the 



\--Moutrt 



"Excretory 

 opemrrs 



FIG. 128. The earthworm. (Sedgwick and Wilson.) 



ground, it will start to crawl away or bore into the soil. Observe 

 that the end that is foremost is tapering. This is the anterior end. 

 The opposite or posterior end is broader and considerably flattened. 

 The part of the body on which the worm crawls is the ventral sur- 

 face, which is somewhat flattened, while the dorsal surface is rounded. 

 The whole body is composed of rings or segments. About one third 

 of the distance from the anterior end of the worm several of the seg- 

 ments are usually somewhat enlarged and form the girdle. 



At the anterior end toward the ventral surface, there is a small 

 opening. This is the mouth, and through it the earthworm sucks 

 in its food which consists not only of dirt, but of leaves of various 

 kinds. Overhanging the mouth is a tiny projection, the lip. The 

 animal has no special breathing organs. The skin, however, is 

 permeated with capillaries, and thus serves as a breathing organ. 



Locomotion is brought about by alternately lengthening and then 



