96 OLIGOCHAETA 



wird. Man kann indess jeden Zweifel dadurch heben, dass man bei massiger 

 Vergrosserung die natlirliche Spitze eines feinen Haares von der Tuba aus in das 

 Blaschen eindringt. Dies gelingt ohne Schwierigkeit und man sieht unter dem 

 Mikroscope deutlich wie die Haarspitze an der hinteren Wand des Blaschens 

 angelangt sich umbiegt. In den meisten Fallen fand ich in demselben Eier, 1-5 

 an der Zahl, von gleicher Beschaffenheit und grosser, als die im Ovarialzipfel 

 enthaltenen und es liegt nahe, es als einen kleinen Eihalter anzusehen, in dem 

 sich die Eier ansammeln, urn dann gemeinschaftlich in eine Eikapsel entleert zu 

 werden. Der grosse Gefassreichtum cles Organes weist auf Absonderung einer 

 Fliissigkeit bin, die vielleicht den Transport der Eier durch den Eileiter erleichtert. 

 Der letztere ist ein mit zahlreichen Gefassen umstrickter Kanal, ausgekleidet von 

 einem, &C. 1 ' 



The development of these egg-sacs in Lumbricus has been studied by BKRGH (5); 

 he has shown that they originate as thickenings of the septum xiii/xiv, which later 

 become excavated and communicate with the cavity of the thirteenth segment by 

 a small aperture ; their interior is broken up, by anastomosing trabeculae, into 

 numerous compartments which lodge the ova ; the oviducal funnel just reaches the 

 interior of the sperm egg-sac as is shown diagrammatically in the sketch given 

 by GOEHLICH : this clearly facilitates the passage of eggs from the sac to the 

 exterior. The investigations of BERGH already referred to have plainly shown that 

 the egg-sacs are quite homologous structures to the sperm-sacs ; both have the same 

 minute structure and originate in the same way. 



The cavities of the egg-sacs are of course portions of the coelom, and they are 

 lined like the rest of the coelom by peritoneal epithelium ; the rest of their walls is 

 muscular tissue. 



In other genera of earthworms egg-sacs are to be found ; but it is doubtful, in 

 some cases at any rate, whether they have any function and are not rather to be 

 regarded as rudimentary organs. Thus in Criodrilus egg-sacs exist ; the ova found 

 in the interior are according to COLLIN 2 (1) smaller than the ripe ova within the 

 ovary itself; this may argue that the ova become degenerate in the egg-sacs or 

 perhaps that this sac is a sort of forcing house for the ova only the comparatively 

 unripe ova finding their way thither to attain maturity ; the fact that the egg-sacs 

 have abundant blood-vessels in their walls, which indeed often renders them 



1 These egg-sacs were passed over by both LANKESTEB (8) and CLAPAR{:DE (r, in their accounts of the 

 structure of Lumbricus ; HOKST, on the other hand, lias described and figured them (11). And they have 

 been recognized by all subsequent observers. 



3 Who figures as an abnormality the egg-sac of one side of the body depending from septum xiii/xiv 

 into the interior of the thirteenth segment. 



