THE EARTHWORM. 135 



These secrete a milk-white fluid of unknown function, 

 containing carbonate of lime. 



4. The crop, a thin- walled dilatation of the alimentary 

 canal in segments 15 and 16. 



5. A muscular gizzard, lined with membranes elevated 

 in chitinous ridges, usually occupying segments 17 to 19. 

 This is the principal organ for grinding and comminuting 

 the food. 



6. The remainder of the alimentary canal is the intes- 

 tine. It probably possesses digestive functions through- 

 out its length. 



II. Organs of Reproduction. Cut the alimentary canal 

 in two at the back of the pharynx. Leave the pharynx 

 in place, but remove the remainder of the digestive tract. 

 After it is lifted out from between the lateral lobes of 

 the seminal vesicles, these organs will be fully exposed. 

 These cover the male reproductive organs ; and a pair of 

 ducts extend backward from them, to open to the exterior 

 at the pores already noticed on segment 15. 



The earthworm is hermaphrodite, and ovaries will be 

 found (sometimes with difficulty) on the floor of the 

 body, a pair of minute, whitish bodies on either side 

 of, and close to, the median ventral line of segment 13. 

 The disconnected oviducts, posterior to the ovaries, pene- 

 trate the septum between segments 13 and 14, and open 

 to the exterior at the pores already noticed on seg- 

 ment 14. 



Attached to the septa, between segments 9 and 10 

 and 10 and 11, are two pairs of minute, whitish sacs, 

 which open, directly downward. These are the seminal 

 receptacles, the accessory organs of reproduction already 

 noticed. In them the sperms from another individual are 

 stored until the time when the eggs are laid ; for, though 

 the earthworm is hermaphrodite, cross-fertilization seems 

 to be the invariable rule. 



