140 Transactions. — Zoology. 



" Spermathccce. — Pelodrilus is furnished with a single pair 

 of spermathecse, in segment viii. Each opens close to the 

 boundary-line between segments vii. and viii., at a spot cor- 

 responding to the male apertures — i.e., between the dorsal and 

 ventral seta3, though nearer to the latter. The spermathecae 

 are very large, and each is doubled upon itself. I usually 

 found clumps of small spherical granular cells, each with a 

 minute but darkly -staining nucleus near to the blind extremity 

 of the spermathecas. I am uncertain whether or not to regard 

 these as parasites. 



" There can be, I think, little doubt that Pelodrilus should 

 be included in the family Phreoryctidce. It agrees with 

 Phreoryctes in the following assemblage of characters : 

 (1) Testes in x. and xi. ; (2) sperm-ducts, two pairs opening 

 separately ; (3) atrium absent ; (4) spermathecas anterior to 

 testes ; (5) hearts long, thin, and much convoluted. The 

 more important points of difference between Pelodrilus and 

 Phreoryctes are these : (1) Sperm-ducts greatly coiled, both 

 on each side opening upon the twelfth segment, though sepa- 

 rately ; (2) only one pair of ovaries in xii., and one pair of 

 oviducts opening between xii. and xiii. ; (3) the presence of 

 septal glands ; (4) nephridia present in some of the genital 

 segments ; (5) clitellum occupying only three segments (xi.- 

 xiii.), and developed only ventrally ; setae of segment xii. 

 absent ; (6) some of anterior septa thickened. These struc- 

 tural characters of Pelodrilus do not indicate much affinity 

 to any other group of the lower Oligochceta. The greatly- 

 coiled sperm-ducts recall those of the Tubificidce and Enchy- 

 trceidce, but other characters do not permit of the establish- 

 ment of any close relationship between Pelodrilus and either 

 of these two families. On the other hand, it does seem pos- 

 sible to indicate some relationship between Pelodrilus and 

 the higher Oligochceta (earthworms), though these are not 

 sufficiently pronounced to admit of a comparison between 

 Pelodrilus and any particular family or families of that 

 group. 



" The general resemblances to the higher forms, other than 

 those shared by Phreoryctes, are as follows : (1) Persistence 

 of nephridia in certain of the genital segments (this is shared 

 by Lumbriculus) ; (2) several of anterior intersegmental 

 septa greatly thickened ; (3) one of the pairs of vasa de- 

 ferentia traverses two segments between the internal and 

 external orifice. Phreoryctes itself comes nearer to earth- 

 worms than does any other genus among the lower Oligochceta, 

 and Pelodrilus serves to increase the closeness of the family 

 Phreoryctidce to the higher Oligochceta." 



