448 Illinois State Laboratory of Natural History. 



due to the glandular peritoneal layer which is formed of 

 much-elongated cells. 



The spermiducal chamber, already mentioned, is formed 

 by an invagination of the mid- ventral wall 'of XI posterior to 

 the middle of the somite. Its lateral walls are connected 

 with the body wall by muscular strands which control their 

 movements. When the form of this chamber is normal the 

 innermost part is transversely elongated, and the outer part 

 has its greatest length parallel with the long axis of the body ; 

 but at times the lateral walls may be pulled far apart, the 

 chamber thus becoming mereiy a ventral depression. It 

 seems probable, therefore, that the structures are chiefly 

 functional during copulation. The wall of the chamber 

 includes a cuticula, continuous with that of the body wall, 

 a layer of hypodermis but slightly modified, and a layer 

 beneath the hypodermis which is quite thick and includes 

 many large cells, perhaps of a glandular nature, the contents 

 of which are usually nearly transparent, though sometimes 

 of a granular character. The peculiar genital setse already 

 referred to as constituting the ventral bundles of XI are 

 borne on the posterior wall of the spermiducal chamber, into 

 which they project. 



But one sperm-sac is present. It extends from its opening 

 in the dorsal part of septum X/XI into XY or XVI. In the 

 somites posterior to XI it is included in the ovisac. The 

 anterior septum of X is sometimes pushed far forward into 

 IX, but there is no anterior sperm-sac. 



Ovaries are present in the usual situation, in the anterior 

 part of XL The ovidueal funnels and oviducts are small but 

 fully developed, and situated between XI and XII. The 

 single ovisac extends backwards from its opening in the 

 dorsal part of septum Xl/XII into XVII or XVIII. The ova 

 develop in the same manner as in the majority of the Tubi- 

 ficidce, and not as in Ilyodrilus and Naidomorpha. 



Two spermatheese are present in the anterior part of X. 

 Each of them has a sac, nearly spherical in outline, which 

 communicates with the exterior through a short duct (PI. 

 XL., Fig. 7) opening on the anterior margin of X at a point 



