282 MR FRANK E. BEDDARD 



L'litcllum,* it is not possible to be certain about this point, though the male organs had 

 every appearance of having arrived at full maturity. 



§ Vas Deferens. 



Phreodrilus is furnished with only a single pair of vas deferens funnels situated in 

 segment XL The funnel of one side is illustrated in fig. 2. It is comparatively small 

 and markedly cup-shaped. The funnel is lined by a single layer of epithelial cells, 

 which are furnished with particularly long cilia. The length of the cilia is only paralleled 

 in the case of ChcBtogaster. The funnel on each side of the body is connected with the 

 vas deferens, which is a narrow tube lined by comparatively few cells (see fig. 2). In each 

 case the vas deferens passes back from the funnel, and then bends round towards the septum 

 separating segments XI and XII ; from this point it runs obliquely backwards, and then 

 is bent upon itself and runs forwards along the side of the sac surrounding the atrium ; 

 near to the ventral side of the body (see fig. 7), where the atrial sac terminates, the 

 vas deferens perforates the muscular sac of the atrium ; in the atrial sac it becomes greatly 

 convoluted, and I have found it impossible to make an accurate diagram of these 

 convolutions. Near to the opening of the vas deferens into the atrium the cilia disappear, 

 and the cells become slightly different in character. This portion of the vas deferens is 

 illustrated in figs. 11, 12. 



In longitudinal sections, a large portion of the Xlth segment lying anterior to the 



circumatrial sac, is occupied by a highly convoluted tube of a different histological 



structure from the vas deferens. This tube is, in the first place, of considerably greater 



calibre than the vas deferens, and cannot, therefore, be confounded with it ; its diameter 



is perhaps three times that of the vas deferens. The structure of the tube is as follows : — 



The outer coat is formed by a layer of muscles arranged in a circular direction, and 



covered externally by a peritoneal layer, or at least by a number of nuclei, which in all 



probability belong to peritoneal cells ; inside is a single layer of epithelium, which is so 



thick as to leave for the most part only a very restricted lumen. The width of the lumen 



was found to vary in different parts of the tube. The epithelial cells are very granular, 



and thus contrast with the epithelium of the vas deferens, which is not at all granular. 



This tube ends blindly in the neighbourhood of the vas deferens funnel ; not, however, in 



the Xlth segment, but in the Xllth, just behind the septum. It is a little dilated 



at the blind extremity, and the cells are here a little more unevenly granular. The tube 



is entirely confined to the Xllth segment. When followed out it is seen to approach the 



ventral extremity of the circumatrial sac. At this point it becomes narrower, and the 



epithelium lower ; it perforates the sac, and becomes continuous with the vas deferens, 



lying in the interior of the sac close to the junction of the latter with the part that lies 



outside the sac. Here and there the interior of this blind sac contains a small mass of 



darkly stained refracting substance, which is probably the excretion of the epithelium. 



* See, however, p. 290, footnote. 



