ANATOMICAL STRUCTURE OF KERRIA. 297 



which however does not connect with the interior of the 

 body. In examining the inner or outer surface of the 

 zone this depression appears transparent, compared to 

 the thick and dark edgings of the zone. The segment- 

 ations of the somites end prominently on the genital zone 

 and the edges are furnished with perforated papillae 

 of very minute size, and with a few epidermal appendages 

 almost as wide as the body-wall. The inner setae 

 of the inner couple are fairly outside of the genital zone, 

 w^hile the outer setse of the same couple are entirely in 

 the zone and situated very close to the prostate and male 

 pore. In Kerria McDonald i the seta; are all present, 

 while in Kerria zonalis the outer setee in the inner couples 

 of somites xvii and xix are wanting. In Ocnerodrilus no 

 similar zone is found. The nearest approach to one 

 is seen in Ocnerodrilus limicola, in which species the 

 clitellum projects down to the male pore in somite xvii. 

 In Gordiodrilus the zone, according to Beddard, is me- 

 dian and ventral, there being only one transparent de- 

 pression between the genital papilla?, on the edge of 

 which the four prostates as well as the two male pores are 

 opening. The single genital zone must then correspond 

 to the two zones and to the tubular groove between 

 them in Kerria. In fact in Gordiodrilus the two zones 

 and tubular cavity of Kerria must have been fused into 

 one single zone. 



The epidermal lining of the central papilla of the gen- 

 ital zone is furnished with a small number of paddle-like 

 appendages, in reality probabl}' only parts of the zonal 

 hypodermis which through ultra development have become 

 separated from the papilla. They are quite small and 

 their structure is not quite plain, with an interior cellular 

 network. In size they are as long as the body-wall is 

 wide and they vary in number. 



