122 
PRANK E. BEDDARD. 
Acanthodrilus, Digaster, &c., as equivalent to the pros- 
tates (“ Cementdriiseu ”) of the Tubificidae, and therefore by 
implication different from the analogous glands in Eudrilus 
and Pontodrilus, which may possibly represent the atrium of 
the Tubificidae. These views are naturally put forward with 
some little hesitation. 
I am disposed partly to agree and partly to disagree with 
Vejdovsky's conclusions. 
I entirely agree with his opinion that the so-called prostates 
in Eudrilus and Pontodrilus are the homologues of the 
atrium in the Tubificidae; I shall, however, bring forward 
reasons for believing that the prostates in Acanthod rilus, 
Perichaeta, &c., are the homologues of those of Eudrilus, 
and therefore also of the atrium in the Tubificidae and other 
families of the “ Limicolae.” 
In Eudrilus I have been able to show (6) that the vasa 
deferentia open into the interior of the large glandular body of 
the seventeenth segment. The relation therefore of the vasa 
deferentia to this body is precisely that of the vasa deferentia 
to the atrium in the aquatic forms. It is true that the vasa 
deferentia are not connected with the extremity of the sup- 
posed atrium as in Monili gaster, Stylaria, &c. ; but in the 
Lumbriculidae the vasa deferentia also communicate with the 
atrium about half way down. 
The atrium consists of two regions — of a glandular portion 
and of a muscular tube prolonged into a penis. This differen- 
tiation of the atrium has its counterpart in the Tubificidae, 
and, moreover, the invaginated penis sheath of the latter is the 
equivalent of the “bursa copulatrix” of Eudrilus. The atrium 
in both consists of an epithelial lining and a muscular layer. 
The epithelial lining is more complicated in Eudrilus than in 
Tubifex ; in Tubifex and apparently in the Limicolous forms 
generally the lining epithelium of the atrium is a single layer of 
ciliated cells : this condition, minus the cilia, is retained in 
Moniligaster. In Eudrilus the lining epithelium of the 
atrium has the complicated structure which I have already 
described. There is undoubtedly a close agreement in struc- 
