ARRANGEMENT OF TISSUES. 



91 



These six kinds of tissue constitute tlie main Imlk of the 

 earthworm, as of liigher animals generally ; hut there are \n ad- 

 dition other tissues which will be treated of hereafter. 



Arrangement of the Tissues. The sini})lest and most diivct 

 mode of discovering the arrangement of the tissues is hv the nji- 

 croscopical study of thin transverse or longitudinal sections. A 



am 



pe 



Ftg. 39.— Transverse section of the body behind the clitellum. a.(\ caN-ity of the ali- 

 mentary canal ; c, cuticle ; em, ccelom ; cm, circular muscles ; c.r, cinular vessel ; 

 ci.u, dorsal vessel; luj, hypodermis; l.m, longitudinal muscles; ».r, ventral nerve- 

 chain; p.e, peritoneal epithelium; s, seta; s.y, setigerous gland; nA.v, sub-intes- 

 tinal vessel ; s.w, muscle connecting the two groups of setae on the same aide ; f j/, 

 typhlosole. 



transverse section taken throuo^h the rei^ion of the stomach- 

 intestine is represented in Fig. 39. Its composition is as 

 follows : — 

 A. Body -WALL. 



This consists of five layers, viz. (beginning with the out- 

 side), — •* 



1. Cuticle ((?). A very thin transparent nieml)rane. not 

 composed of cells and perforated by fine pctres. It is a product 

 or secretion of the — 



