STRUCTURE OF TWO NEW GENERA OP EARTHWORMS. 265 



either side of the ventral line ; the thickening ceases at the 

 first seta. 



A curious fact in relation to the atria is the connection of 

 the nephridia with these organs. In the other segments of the 

 body the nephridia open in front of the lateral setse ; but in 

 the 17th segment the duct of the nephridium traverses 

 the ventral body-wall in an oblique direction, and 

 joins the atrial duct just before its opening into the 

 external depression already spoken of (fig. 40). As this 

 occurred on both sides of the body it does not seem likely to 

 be an abnormal condition characterising the individual only, 



§ Summary of more important facts in the structure of Helio- 

 drilus and Hyperiodrilus. 



(1) The epidermis is furnished as in other Eudrilidse, and in 

 that family alone, with peculiar organs possibly of a sensory 

 nature ; these consist of a central nucleated core surrounded 

 by many nucleated sheaths ; the organs have a certain resem- 

 blance to Pacinian bodies of Vertebrates, and are scattered 

 irregularly over the surface of all the segments save the first. 



(2) The alimentary canal has a single pair of large lobed 

 calciferous glands in the 13th or 14th segment; in each of 

 Segments 10, 11, 12, is a median diverticulum of the oeso- 

 phagus, of which the epithelium is much folded, so that it 

 presents the appearance of a series of parallel tubes ; peri- 

 pherally the cells themselves are excavated, and form a rami- 

 fying system of ductules ; the pouch of Segment 10 is smaller, 

 and the foldings are much simpler and do not anastomose. 

 There is no anterior gizzard, but six gizzards, one to each 

 segment, at the junction of the oesophagus with the intestine. 



(3) The supra-intestinal blood-vessel in the oesophageal 

 region is enclosed in a special coelomic compartment, which is 

 almost filled by deeply staining nucleated corpuscles. 



(4) The male genital pore is single and median upon 

 Segment 17. The ''atria" are glandular and very long; in 

 Heliodrilus the vasa deferentia open into them in both 

 genera. In neither are there any penial setae, but in Hype- 



