102 ECONOMIC ZOOLOGY AND ENTOMOLOGY 



no special organs of respiration, but the thin walls of the skin 

 are traversed by a network of minute blood-vessels which 

 are separated from the air by only a very thin membrane 

 through which the oxygen passes readily and the carbon 

 dioxide is given off. 



nephridium f^rsal ttotd vessel 



\ hepatic cells / 



\ \ i longitudinal muscle 



'. \ / firmlnr miiscle fit 



I/ 



ft jcircular muscle fibres 

 epidermis 

 .cuticle 



typhlosole 



nephridipore ! nephrostome \ 



ventral vessel 



body cavity 



FIG. 38. Cross-section of earthworm. 



The earthworm is hermaphroditic, that is, both spermatozoa 

 and ova are produced in the same individual. The testes are 

 two pairs of flattened glands lying in the region of the tenth and 

 eleventh segments. These are connected with the seminal 

 vesicles and communicate with the exterior through the long 

 vasa deferentia which open in the fifteenth segment. The ovaries 

 are attached to the septa separating the twelfth and thirteenth 

 segments. The ova reach the exterior through a pair of funnel- 

 shaped oviducts, the mouths of which are near the ovaries. 



