THE EARTHWORM AND ANNELIDS IN GENERAL 167 



or chemical injury; numerous fine pores allow the secretions from 

 unicellular glands to pass through (Fig. 86). Under the micro- 

 scope it is seen to be marked with very fine stria which cross one 

 another; they cause the surface of the body to appear iridescent. 

 A number of external openings of various sizes allow the en- 

 trance of food into the body, and the exit of faeces, excretory prod- 

 ucts, reproductive cells, etc. (i) The mouth is a crescentic 



FIG. 86. Vertical section of a bit of epidermis of the earthworm. Four 

 mucus cells in different stages of secretion. Mucus is passing through 

 one of the two pores in the cuticle, cu. (From Dahlgren and Kepner.) 



opening situated in the ventral half of the first somite; it is over- 

 hung by the prostomium. (2) The oval and aperture lies in the 

 last somite. (3) The openings of the sperm ducts or vasa deferen- 

 tia are situated one on either side of somite XV. They have 

 swollen lips; a slight ridge extends posteriorly from them to the 

 clitellum. (4) The openings of the oviducts are small round pores 

 one on either side of somite XIV; eggs pass out of the body 

 through them. (5) The openings of the seminal receptacles 

 appear as two pairs of minute pores concealed within the grooves 

 which separate somites IX and X, and X and XI. (6) A pair of 

 nephridiopores (Fig. 85, ext. neph.), the external apertures of the 

 excretory organs, open on every somite except the first three 

 and the last. They are usually situated immediately anterior tc 

 the outer seta of the inner pair. (7) The body cavity (Fig. 85 



