1918.] J. Stephenson : Oligochaeta of the Inle Lake. 



13 



{v^ the wider, eetal portion of the atrium has a generally vertical 



course to the exterior through the coelomic sac ; 

 (vi) the paratrium, a narrow tube ending bhndly at its ental end 

 and ioining the atrium at the other ; it is also covered by a 

 thick layer of modified peritoneal cells. 



In all the cases hitherto observed the male orifice was quite simple 

 (Beddard, 2 ; Michaelsen, 5 ; Stephenson, 9). 



I may observe, first, that the ectal portion of the atrium is here 

 divisible into two distinct sections, — a lower, the terminal part of the 

 whole deferent apparatus, and an upper ; the distinction is, I beHeve, of 

 some importance from the point of view of the protrusion of the penis. 

 The upper section makes several bends in the upper part of the coelomic 

 sac ; the epithelium lining the lumen is cubical, and the peculiarity of 

 the cells is that the inner portion stains slightly or not at all, — less deeply 

 than the basal part ; the hyaline appearance of the part of the cells 

 which is towards the lumen gives them a distinctive character ; the 

 nuclei are spherical, and stain rather Hghtly, showing scattered grains of 

 chromatin in their interior. This section is divided from the lower 

 usually by a distinct narrowing, and sometimes the walls of the tube 

 appear folded here. The lower section has a generally vertical position 

 in the sac ; its muscular coat is thick, and the epithelium is columnar, 

 though of irregular height ; the nuclei are oval, and stain densely. 



/JCP.. 



at.&TL. cs. 



1. — Branchiura soicerhyi ; male genital apparatus, diagrammatic, at. ec, at. en., 

 at. m., the ectal, ental, and middle portions of the atrium ; b., body wall ; 

 C.S., coelomic sac ; /., funnel ; in., muscular band ; p. at., paratrium ; per., 

 mass of peritoneal cells; s., septum 10/11 ; v. d., vas deferens ; $, male 

 aperture. 



There are also a few other minor differences between these specimens 

 and those investigated by Michaelsen. Thus the middle does not 



