96 OLIGOCHAETA 



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

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

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

 Mikroscope deutlich wie die Haarspitze an der hinteren Wand des Blaschens 

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

 an der Zahl, von gleicber Beschaffenbeit und grosser, als die im Ovarialzipfel 

 enthaltenen und es liegt nabe, es als einen kleinen Eibalter anzuseben, in dem 

 sicb die Eier ansammeln, um dann gemeinscbaftlicb in eine Eikapsel entleert zu 

 werden. Der grosse Gefassreichtum des Organes weist auf Absonderung einer 

 Fliissigkeit bin, die vielleicbt den Transport der Eier durcb den Eileiter erleicbtert. 

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

 einem, &c.^ ' 



Tbe development of these egg-sacs in Lwmhncus bas been studied by Bergh (5); 

 be bas sbown tbat tbey originate as thickenings of tbe septum xiii/xiv, which later 

 become excavated and communicate with tbe cavity of tbe 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 tbe 

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

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

 exterior. Tbe investigations of Bergh already referred to have plainly sbown tbat 

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

 minute structure and originate in the same way. 



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

 lined like tbe rest of tbe coelom by peritoneal epithelium ; tbe 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; tbe ova found 

 in tbe interior are according to Collin ^ (1) smaller than the ripe ova within tbe 

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

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

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

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



1 These egg-saos were passed over by both Lamkestek (8) and Clapakede (1) in their accounts of the 

 structure of Lumiricus ; Horst, on the other hand, has described and figm-ed them (11). And they have 

 been recognized by all subsequent observers. 



2 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. 



