Dr. F. E. Beddard on the Genus Trichodrilus. 235 



I term this species, i£ it be accepted as undescribed, Tricho- 

 drilus icenorum, after the plan of nomenclature initiated for 

 the genus by Clapare le. 



To determine whether this subterranean species is or is not 

 identical with Trichodrilus allobroc/um of Claparede is very 

 difficult on account of the incomplete description given by 

 that naturalist. I do not find it possible to come to any con- 

 clusions as to differences in the form of the spermatheca and 

 atria in the two forms. It would seem, however, that the 

 vascular and excretory systems do offer differential characters. 



I do not think that there is room for error in the quite 

 diverse descriptions given above of the appendages of the 

 dorsal vessel which were lacking in the examples of this 

 Trichodrilus examined by myself, and are fully figured and 

 described by Claparede. Furthermore, that author is detailed 

 in his account of the nephridia of the early segments of the 

 body, and his descriptions differ from what I have seen 

 myself ; the doubts, therefore, which I have expressed above 

 may be unnecessary. The slender looping of the nephridia 

 in the Swiss species seems also to be different from the 

 closely packed and rather numerous coils which I found in 

 the nephridia of the worm from Norfolk. 



There can be, as I think, no doubt that both Bretscher* 

 and Piguet f are right in distinguishing Trichodrilus san- 

 guineus as a species different from that of Claparede. Nor 

 can I identify it with the form described here by myself. 

 The possession of only one pair of spermatheca} seems to be a 

 sufficient mark of specific distinctness. Moreover, this form 

 is a smaller one, measuring only up to 13 mm. as compared 

 with 14-25 mm. 



This leads at once to the question of the identity or 

 non-identity of the genera Trichodrilus and Phreatothrix, for 

 the main difference between the two genera, according to 

 Vejdovsky J, is the presence of two pairs of sperrnathecaj in 

 the former genus, while Phreatothrix has only one pair 

 of these organs in the eleventh segment, the second pair 

 disappearing at maturity. This latter statement does not, 

 however, apply to the species which I found myself in water 

 from a well at Cambridge. In this species § there was but 

 one pair of the organs, and no trace of the smaller pair of 

 Phreatothrix prayensis. Vejdovsky is doubtless correct in 

 noting a protrusible penis in Phreatothrix; but is it so clear 



* Rev. Suisse Zool. vol. viii. p. 444. 

 t Loc. cit. vol. xxi. p. 141. 

 \ Zeitschr. wiss. Zool. t. c. 

 § Proc. Zool. Soc. t, c. 



