566 FRANK E. BEDDAED. 



Dot continued on to tlie epithelium which lines the atrium. 

 At the orifice of the vasa deferentia they are particularly long, 

 and project for some way into the interior of the atrium. In 

 Libyodrilus, therefore, the atrium has come to be, as it is in 

 such worms as Nais, a kind of continuation of the vasa 

 deferentia. Among the Eudrilidse the point of opening of the 

 vasa deferentia gradually moves down the atrium until, in 

 Nemertodrilus, it comes to be placed near to the external 

 orifice. 



This series of facts lends further support to the original 

 suggestion of Vejdovsky, which was strengthened by my own 

 observations, as to the homology between the atrium of the 

 aquatic genera and the prostates of the terrestrial genera. 



If we are to follow Dr. Benham (11) in objecting to this 

 identification we shall be plunged into obvious difficulties, for 

 Dr. Benham considers '^ that a portion of the prostate in 

 Perichgeta, Eudrilus, and other genera, in which the sperm 

 duct and the prostate join, is probably the homologue of the 

 atrium of Tubifex." 



I should mention that the interior of the atrium in Libyo- 

 drilus is not divided by a septum, and that the lining epithe- 

 lium is greatly folded ; this is carried to such an extent that in 

 longitudinal sections the lumen appears to be furnished with 

 tubular diverticula ; transverse sections are required to show 

 that these are merely foldings of the epithelium. 



§ Female Reproductive System. 



The extraordinary development of coelomic pouches in con- 

 nection with the different parts of the female reproductive 

 system is the most distinguishing character of the Eudrilidse, 

 and also occurs in the present species. 



Spermathecal Sac. — In dissecting the species which 

 forms the subject of the present memoir, the most conspicuous 

 organ of the body is a large sac which lies upon the dorsal 

 surface of the oesophagus. This structure is illustrated in 

 fig. 1, which represents a general view of such a dissection, and 



