ANATOMY, HISTOLOGY, AND AFFINITIES OF PHREORYCTES. 635 



I find that I have not described their actual orifices with complete accuracy in my 

 former note upon this species. 



The first pair of vasa deferentia do indeed open near to the ventral pair of setse 

 between these and the dorsal pair, but the second pair are a little different. The vas 

 deferens of each side is much shorter, and opens well in front of the ventral pair of setse 

 of the Xllth segment, though behind the groove which separates this segment from the 

 Xlth ; that there is really this somewhat unexpected difference between the two pairs 

 of vasa deferentia I have been able to prove by longitudinal sections, which are much 

 better than transverse sections for demonstrating such a point. In preparation of the 

 worm, mounted entire in Canada balsam, some of the orifices of the sexual ducts were 

 quite conspicuous. One of three such preparations which I have shows the external 

 pore of the oviducts, and of the posterior pair of vasa deferentia ; in all three cases the 

 orifices are situated on a line with and in front of the ventral setse ; the oviducal 

 pores are placed further forward than the male pore — in fact, on the intersegmental 

 furrow. 



Although out of the three specimens, in which I have examined the vasa deferentia, 

 only one showed with perfect plainness the apertures of both pairs, the position of the 

 anterior and posterior pairs respectively in each of the two remaining specimens leaves 

 no doubt upon my mind that fig. 1 of the Plate is a correct representation of the position 

 of the generative pores. 



The terminal section of the vas deferens is lined with a chitinous membrane ; this 

 fact is not mentioned in my former paper ; I remark upon it here as it is a further 

 point of similarity between the vasa deferentia and oviducts, which latter are also 

 furnished with a chitinous lining distally. In my former paper I was only able to 

 urge the great probability of the genus Phreoryctes being typically provided with four 

 pairs of gonads and four pairs of independent ducts. I am now able to state this fact 

 with certainty. 



The adult ova (fig. 11) are of very large size; the relation between their diameter 

 and that of the body of the worm is shown in the figure cited. A' comparison of this 

 section with a corresponding one of Clitellio arenarius [Beddard, B 1] shows that in 

 that species the ova are of the same relative size as in Phreoryctes ; they are therefore 

 actually smaller in Clitellio. The larger size of the ova of Phreoryctes is due to the 

 great abundance of yolk, which is present in variously-sized spherules. The ovum is 

 bounded externally by a fine homogeneous membrane ; it possesses a larger deeply 

 staining nucleus, within which is a nucleolus. Vejdovsky [B 4] has recently published a 

 careful description of the ripe ovum of Rhynchelmis. He remarks that the size of the 

 mature ova vary according to the size of the individuals in which they are found, the 

 largest worms producing the largest ova. I have pointed out myself that the relative 

 size of the mature ova of Clitellio and Phreoryctes is about the same ; it is not, therefore, 

 a distinction of any importance that the mature ova of Phreoryctes are larger than those 

 of the Tubificidse (Clitellio). 



