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BIOLOGY 



MICROSCOPIC ANATOMY OR HISTOLOGY 



The body of the earthworm is made of large numbers of 

 cells of great variety in form and structure. The cellular 

 structure in some of the organs of the body can readily be 

 made out under the microscope, but in others the cells can 

 be seen only by special methods. The most important features 

 of the histology are as follows : 



Body Wall. The body wall contains several layers; Fig. 



81. On the outside a very thin cuticle covers the whole body, 



lm 



FIG. 81. DIAGRAM REPRESENTING A CROSS SECTION 

 OF THE EARTHWORM'S BODY 



Showing the microscopic anatomy, 

 cm, circular muscles; 

 d, dermis; 



dv, a branch from the dorsal blood vessel; 

 ep, epithelium; 

 lm, longitudinal muscle; 

 n, nerve; 

 nc, ventral nerve cord; 



ne, nephridium; 



o, opening of the nephridium; 



per, peritoneum; 



s, setae; 



siv, subintestinal vessel; 



ty, typhlosole. 



perforated, however, by numerous openings through which the 

 various secretions pass. Inside of the cuticle is a somewhat 

 thicker layer of cells mainly cylindrical in form, known as 



