138 DR. J. STEPHENSO\ ON THE MORPHOLOGY, CLASSIFICATION, 



of male organs of Desmogaster and the dislocation forwards of all 

 the other sexual organs. Though the difference between the two 

 views is not great, 1 prefer the above wording, for the following 

 reasons : — 



First, the approximation of the septa in the region of the 

 testes is observed in other genera ; it has been noted by Michael- 

 sen in some species of Accmt/iodrilus (15) ; it occurs in Eutyphceus, 

 where septa 8/9-10/11 are usually very close together (testes and 

 funnels have, however, in this genus disappeared from segment x) ; 

 it is seen also in Hoplochcetella (Stephen.son, 24), where septa 9/10, 

 10/11, and 11/12 may be so closely approximated as to appear at 

 first like one hugely thickened septum. 



Next (and this I am inclined to regard as important), the 

 process that I have assumed for Drawida is apparently seen in 

 progress in Syngenodrilus (cf. text-fig. 16), where the two testis 

 sacs are contiguous, indeed fused, and the intervening segment 

 has been squeezed out of existence ventrally, though a portion 

 persists dorsally. 



Lastly, the trabeculse which Benham describes as crossing the 

 testis sac in Moniligaster indicus { = Draioida robusta) (10) may 

 possibly represent the remains of the septum which, on my view, 

 at first separated the cavities of the two sacs after they had come 

 together. It may be added that the existence of a rudimentary 

 second prostate, in front of that belonging to the normal male 

 apparatus, in Draunda willsi (Michaelsen, 13), and of a similarly 

 situated well-developed second prostate in D. raid (Stephenson, 

 26), shows only that the actual funnel and vas deferens of 

 Drawida are the equivalent of the posterior pair of Desmogaster ; 

 the testis may quite well be the anterior testis, as I have supposed, 

 and the testis sac the product of fusion of the original two.* 



(4) The Numbering of the Segments in Desmogaster. 



The segments i, g, /«,/, e (text-figs. 11 k 12) correspond in Bes- 

 mogaster and Eupolygasler ; and on the view here advocated, i 

 and h correspond in Desmogaster and Draioida (text-figs. 1 1 & 13). 

 Now i-e are segments viii-xi, with the anterior testis sac, in 

 Desmogaster, and vii-x, with the testis sac, in Eujyolygaster ; 

 i a,nd h are viii and ix in Desmogaster, vii and viii in Eupoly- 

 gaster and Drawida. That is to say, the whole of the sexual 

 organs are one segment farther forward than they ought to be in 

 Eupolygaster and Drawida. 



It would be easy arbitrarily to suppose that a segment in the 

 anterior part of the bod\" had somehow been lost in the ancestors 

 of these two genera, or, with Michaelsen, to assume a " dislocation 

 forwards " of the sexual organs (which comes to much the same 



* It maj- be said that if it is the posterior vas deferens which persists in Dratvida, 

 the persistent spermatheca should be the anterior and not the posterior. This is not 

 iiecessarj', however ; as ah-eady stated, there are species of I)esmogast€r v!\\.\\ two 

 pairs or with only one pair of spermatliecaj ; in the latter case, the single pair of 

 spermathecse may be the anterior or the posterior. In D. schUdi it is the posterior ; 

 if such a form were to undergo the assumed squeezing together and fusion of the 

 testis sacs, the exact condition oi Draivida and Moniligaster would be arrived at. 



