DESCRIPTIONS OF GENERA AND SPECIES 233 



In all the Tubificidae the vas deferens of each side opens into a terminal chamber, 

 ■which I propose to call the spermiducal gland, abandoning the term atrium ; a portion of 

 this is commonly exsertile, and forms a penis. The simplest form of the gland is seen 

 in Ilyodrilus ; there is in /. coccineus (woodcut, fig. 39) a simple globular sac, which 

 receives the sperm-duct ; the sac is lined with ciliated epithelium, outside of which 

 is a feebly developed layer of muscle, covered again by a mass of large granular cells. 

 This suddenly narrows into a duct which leads to the exterior ; it is not exsertile, but 

 special muscles allow of the protrusion of this duct along with the epidermis of the 

 body. Stolc figures (3, Tab. iii. fig. 1) a conical eminence of the body, well within 

 which lies the duct. The resemblance of this chamber to that of the Naidomorpha 

 and of the Lumbriculidae and Moniligastridae has already been pointed out. 



Branchiura , has an efferent apparatus which, besides possessing peculiarities of its 

 own, is in some respects intermediate between Ilyodrilus and other Tubificidae. 



The terminal chamber itself is apparently much as in Ilyodrilus, only the lining 

 epithelium does not show any ciliation, and the other layers are thicker. The principal 

 difference is that the vas deferens joins the atrial duct just above the penis. This 

 is also the case in Hesperodrilus ; this duct is long, and differentiated into two 

 regions ; it has at first a flattened, ciliated epithelium ; this, changing abruptly, 

 becomes taller, thrown into slight folds, and not ciliated. The whole duct is surrounded 

 by muscles, and there is some evidence that the distal part of the tube is eversible. 

 In any case the distal part of the tube, being of a different structure from the 

 restj may be termed the penis. 



In all the remaining Tubificidae there is an extrusible penis, and the spermiducal 

 gland is rather different in structure, being, moreover, in every case, except Clitellio 

 and Hesperodrilus, furnished with one (Tubifex, Limnodrilus, &c.) or many (Telmato- 

 drilus) prostates (' Cementdriisen,' ' Kittdriisen '). The simplest state of affairs is 

 found in Limnodrilus, and, in fact, in all genera except Tuhifex. In Limnodrilus 

 the terminal chamber is long, narrow, and somewhat pear-shaped, being swollen 

 where it receives the sperm-duct. Its lining epithelium, like that of the vas deferens, 

 is ciliated ; outside this is a layer of muscular fibres, and outside this, again, a peritoneal 

 covering. At one side, near the upper extremity, is a lobate gland, the prostate, 

 attached to it ; this gland, which has been variously termed ' prostate,' ' Kittdriise,' 

 ' Cementdriise,' ' v^sicule seminale,' is solid and compact, and composed of pear-shaped 

 granular cells; where it is attached to the terminal chamber, the muscular and 

 peritoneal layers of the latter disappear, so that the cells of the gland are in actual 

 contact with the epithelium of the terminal chamber. This is well shown in 

 Clapabede's figures (2, PI. i. figs, i and 4) of L. hoffmeisteri and udekemianus. 



Hh 



