THE ANATOMY. SPERMIDUCAL GLANDS 119 



(4, p. 385) with regard to Dekmoga&ter : he pointed out that in the worm the outer 

 layer of glandular cells were imbedded in a stratum of muscle, and that the atrium 

 was so far intermediate between that of Moniligaster and Acantkodrilus, &c. ; the 

 muscles had not quite got to divide the two epithelial layers clearly from each 

 other. Still, of course, this does not take away from the closer resemblance of the 

 gland of Moniligakter to that of the Lumbriculidae than to that of the terrestrial 

 earthworms. The occasional though rare ciliation of the lining epithelium in Eudrilidae 

 removes all the differences that separate the spermiducal gland of the higher from 

 that of the lower Oligochaeta. It will be seen therefore that the ' prostate ' of 

 Penrhaeta may be safely compared with the ' Cementdriise ' of Tubifex without doing 

 any harm ; but that the insistance upon this homology must not be carried so far as 

 to obscure the other obvious relations between the spermiducal glands of different 

 forms. 



A question which now requires consideration is the origin of the spermiducal 

 glands ; are they to be regarded simply as dilatations on the sperm-duct or as 

 separate structures which have come to have a relation to the sperm-ducts ? I incline 

 to the latter view. The chief reason which leads me to take up this position 

 is the existence of supplementary glands which have no relation to the sperm- 

 ducts ; in Dichogaeter damonis the two segments following that upon which 

 the sperm-ducts open are each furnished with a pair of tubular glands exactly like 

 the spermiducal glands in structure, but rather smaller : it is also remarkable 

 to find that these two pairs of glands open on to the exterior in exactly the 

 same position as those of the seventeenth segment, and that the ventral setae of 

 their segments, as of the seventeenth, are missing ; nothing in fact is wanting to 

 complete their likeness to spermiducal glands, except that they have no direct 

 relation to the sperm-ducts. The occasional presence of two pairs of glands to only 

 a single pair of male pores, as we find in Acanthodrilus, Gordiodrilus, and Perichaefa 

 ceylonica, is not so remarkable, for in all these worms there are two pairs of distinct 

 sperm-ducts, although they become one at the external pore. This view of the origin 

 of the glands is the one held by ROSA; in a paper upon the structure of Kynotux 

 michaelsenii this author refers the spei-miducal glands to the same category as certain 

 glands found in that species in the segment following, and showing exactly the same 

 minute structure. These glands are accompanied by penial setae. ROSA, it should be 

 stated, is not of opinion that this view can be applied to the glands of other 

 earth-worms ; ho is only considering the Geoscolicidae, which according to him have 

 ' pseudo-prostates,' not comparable to the apparently similar glands in the Oligochaeta 

 generally ; this opinion of ROSA'S is not one that commends itself to me, and I have 



