BY R. VON LENDENFELD, PH.D. 973 



beneath the Epithelium of the canals of the network, which 

 originate from the meridian canals. The latter are a little larger 

 than those in the meridian canals. At a greater distance from 

 these canals, ova are clearly seen, which increase in size the further 

 they are removed from the meridian canals. 



In those parts of the vascular reticulation which occupy the 

 middle of the fields, the canals appear thickly filled with ripe ova. 



From these observations I think I must draw the conclusion 

 that the place of germination of the ova lies in the meridian 

 canals, whilst their maturing place in Neis is removed to the 

 canals of the reticulation. 



Single Entoderm cells of the vieridian canal epitJiel sink down 

 into the suh-einthelium and wander along it into the vascular 

 reticulation. During this migration they increase in size. At 

 length they remain in those parts of the tietwork vessels, furthest 

 removed from the meridian canals and there develope into mature 

 ova. The spermatoza are found united in balls also in the reticula- 

 tion canals. 



As to the origin of male products I have arrived at no satisfactory 

 conclusion. It is of course not impossible that the ova-germs 

 migrate froQi the Ectoderm, first into the subepithelium of the 

 meridian canals, and then continue their migration in the manner 

 described above. But this I do not consider probable. The whole 

 process appears somewhat analogous to the formation and migra- 

 tion of the ova in many Hydromedusaj. (11.) The same cause 

 which Weisman ascribes to the migration of these elements in the 

 Hydroids cannot be accepted for our Ctenophore. I see in this 

 process rather a further development of that met with in Beroe 

 Forskalii. 



The Margin of the Mouth. 



The mouth-margin of Beroe is clothed by a highly developed 

 Ectoderm which Chun (3, pp. 33, 159, 160, Taf. XV., %. 19) and 

 Richard Hertwig (6, pp. 333-337, Taf. XIX., figs, 11, 14, 15, 17) 

 have described and figured. 



The mouth-margin of Neis cordigera resembles that of Beroe in 

 so far as below the free margin the same three zones are met wdth 



