106 



OLIGOCH AETA 



The Lumbriculidae, the Phreoryctidae, the Geoscolicidae (for the most part) have no 

 such glands at all ; and in these worms the sperm-duct is with a few exceptions un- 

 provided with any glandular apparatus at its terminal orifice. 



The simplest form of the terminal chamber is found, as might be expected, in 

 the lower aquatic Oligochaeta ; in the Naids its structure is as follows : the sperm- 

 ducts lead on each side of the body into a pear-shaped sac, which has been called 

 the ' atrium ' and opens on to the exterior in the sixth segment ; this sac is lined by 

 a glandular epithelium apparently without cilia ; externally to this epithelium is 

 a covering of peritoneal cells ; the ' atrium ' in Nais elinguis gradually passes into 

 the sperm-duct ; in Stylaria lacustris and in Dero there is an abrupt break between 

 the two ; I cannot discover any positive statements as to whether the lining cells 

 Fig. 27. are or are not ciliated in the Naidoniorpha ; there is no indication 



of any ciliation in the figures of STOLC (5) and VEJDOVSKY (24). 



Among the Lumbriculidae we meet with a terminal chamber 

 which is modelled upon the same plan as that of the last family. 

 Among the Enchytraeidae there is very commonly a homologous 

 organ of an equally simple, though rather different structure. 

 I follow here MICHAELSEN'S account of Enchytraeus humicultor. 

 It is a rounded or oval body (called by MICHAELSEN a ' penis '), 

 lined with long cells. It communicates with the exterior by a 

 short invagination of the latter, which is beset with groups of 

 unicellular glands. The sperm-duct opens at the summit of the 

 terminal gland which has a muscular layer outside the lining 

 epithelium. 



The Tubificidae have an ' atrium ' which is more complex 

 than that of the last two families. In Tubi/ex itself, which 

 may serve as a type of the family, the organ has been described 

 by a large number of writers ; it is an elongated sac receiving 

 the sperm-duct at one end and opening on to the exterior at 

 the other ; the proximal part is ciliated ; the distal region is 

 not ciliated ; the latter forms a protrusible penis which is 

 described more fully in a separate section (see below). A 

 remarkable feature of the atrium in the Tubificidae, with the 

 exception of a few forms, is the presence of a glandular appendage variously termed 

 'Cement gland' (LANKESTER), ' Cementdriise ' (VEJDOVSKY), 'Prostate' (EISEN, &c.); 

 this is a thick patch of pear-shaped glandular cells whose ducts (merely the pro- 

 longation of the cells themselves) open into the lumen; VEJDOVSKY has shown that 



MALE EFFERENT 

 APPARATUS OF 

 LOPHOCHAETA. 



(After Stole.) 

 i. Funnel. 2. Penis. 3. 

 ' Atrium. ' 4. ' Prostate. ' 

 5 Coiled sperm-duct. 



