1915.] J. STEPHENSON : Indian Oligochaeta. 103 
Nottodrilus | 
(or primitive Acanthodriline; holoandric, 
acanthodriline ¢ apparatus, lumbricine 
setae, Ben spermathecae 2—$.) 
Howascolex | 
(as Notiodrilus, except that meganephridia 
and micronephridia coexist.) | 
Octochaetus 
(as Notiodrilus, except micronephridial.) 
| | 
Eutyphoeus Dinodrilus 
(as Octochaetus, except microscolecine ¢ (as Octochaetus, except commencing 
apparatus; a majority of forms are perichaetine increase of setae.) 
proandric; spermathecae $ only.) 
Hoplochaetella 
(as Dinodrilus, except that perichaetine 
condition fully established.) 
Now if it were allowable to derive the mixed mega- and micronephridiai condition 
of Erythraeodrilus from a pure micronephridial, it would be easy to suppose Erythrae- 
odrilus a descendant of Hoplochaetella,; the evolution would be, in some respects, 
parallel to that which has given rise to Eutyphoeus from Octochaetus. Eutyphoeus has 
undergone the microscolecine reduction of the posterior portion of the male genital 
apparatus; 2.6. of the original two pairs of prostatic glands with openings on xvii 
and xix, those of xix have disappeared, and the ending of the vas deferens, originally 
on xviii and so between the prostatic pores, has approached or fused with the re- 
maining prostatic aperture, that of xvii. Along with this in Eutyphoeus there goes 
the reduction of the spermathecae-to one pair instead of two, and the disappear- 
ance, in the majority of cases, of the posterior pair of testes (proandric condition). 
The same changes appear to be in progress in Erythraeodrilus ; the microscolecine 
reduction has taken place, but it has not as yet been followed by the disappearance 
of the posterior pair of testes ; in the spermathecal apparatus there is a tendency to 
the reduction in the number of apertures, even if this has not actually been attained. 
It is interesting to note the way in which the reduction of spermathecae is being 
brought about ,—those of the same side have approached and met at their external 
ends in the middle of segment vill. In Eutyphoeus (if this genus has really had a 
parallel evolution) we may suppose that after fusion of the apertures, fusion of the 
spermathecae themselves followed; and that then the point of opening of the single 
organ moved forwards to groove 7/8, the situation of the anterior of the original two 
DRE of Rs 
! I use the generic name Notiodvilus i in the sense in which it was used, for te by Michaelsen 
in his ‘‘ Geographische Verbreitung der Oligochaten.’’ 
