370 



lar cells in fact ; no coat of muscle is present except near the external 

 aperture . 



In Trigaster, Megascolides, Perichaeta and other genera, the organ 

 is distinctly divisible into two regions: a distal region, having the above 

 structure (more or less complicated in Perichaeta] , and a proximal 

 region in which the «clitellar« cells are absent, and the epithelium is 

 surrounded by a muscular coat ; the spermduct, in the two latter genera 

 communicates with this proximal region. 



Fig. 2. Pontodrilus, Megascolides &c.: The spermduct (c) and prostate (ò) communicate 



with the atrium (a) at about the same point : the prostate, which is solid in Tuiiifex, 



is now hollowed out and the atrial epithelium is continued up into it. 



^ 



Fig. 3. Perichaeta : The atrium is curved and protrusible : 

 the prostate is branched and lobed. 



In Eudrilus the muscular coat surrounds the whole organ, which 

 presents some points of difficulty in its interpretation. 



In Moniligastei-, the epithelium is surrounded directly by a mus- 

 cular coat, outside which is a thick layer of pyriform cells, with granu- 

 lar contents: so that this organ in Moniligastei' very closely resembles 

 the »atriuma in Stglaria, Tuhifex &c. 



4) Such are briefly the facts: it is in the interpretation of these 

 facts that I differ from Mr. B e d d a r d. He calls all these organs «atria« : 



