804 



ON THE CII.ETOSOMATID.E, 



c?(^.) seems to consist of several concentric ]ainin{i3. AVithin it, is 

 a fine, structureless layer of uniform thickness, below which is a 

 very irregular layer, which ai3pears deep brownish-yellow in all 

 sections w^iich are double-stained with Erlich-hsematoxylin and 

 eosin. In places, this projects into the body-cavity, in the form 



of thickenings, which have 

 no regular arrangement 

 cut. (Fig. 52, S.C.). Extending 

 along the inner surface of 

 int. ^^^® body-wall throughout 

 its length, from pharynx 

 to anus, are four equally 

 si^aced ridges of mesoder- 

 mal tissue (Figs. 51, 52, 

 ni.h.). Just behind the 

 pharynx, these are very 

 prominent, and consist of 

 a loose, vacuolated tissue 

 In 



S.C." 



l.m>.b. 



Fig. 52. — X. fena.v. 



T.fS. through posterior region of trunk 



{ X 950). 



containing large nuclei, 

 the mid-region, the ridges 



are barely distinguishable, 

 but, towards the posterior end, they again become very promi- 

 nent, especially the two lateral ridges, which are here very large, 

 and enclose large spaces which, in places, are almost filled-out 

 with fine granules, staining a deep pink with eosin. 



The body-wall encloses a coelomic cavity (Figs. 51, 52, c(d.), 

 which is extensive in the anterior region of the trunk, but, 

 further back, becomes nearly filled up by the alimentary canal 



and genital organs. 



The alimentary canal extends straight through the body, from 

 mouth to anus. The mouth leads into a muscular pharynx, 

 which is elongated and slender (Fig. 53, ^.>/«.). The j^osterior end 

 is slightly enlarged, but there is no definite bulb. Its walls are 

 one cell thick, the cells being few in number, and very large, with 

 a large nucleus in each. Round its anterior end, is a group of 

 elongated, slender, yellowish bodies, which seem to open into the 



