237 



nation having been performed on any of the Mollusca. When the ex- 

 periment was first performed two or three hours elapsed after bringing 

 the ova and spermatozoa together before fecundation took place. — This 

 was due to the fact, I believe, that the sexual products were not fully 

 matured, for the spermatozoa, when first taken from the testis, were 

 motionless and only showed active movement after having been kept 

 tAvo or three hours in sea-water. A month or six weeks later however 

 (or about the middle of January) spermatozoa were found which were 

 quite active immediately after being removed from the testis, and at 

 that date fecundation took place in from half to three quarters of an 

 hour after mixing the sexual products. 



In order to satisfy myself that we actually had an artificial fecun- 

 dation and not an apparent one, I took the ripe ova from as many as 

 ten females and placed them in separate glasses of sea-water Avithout 

 adding any spermatozoa. After twenty-four hours these ova were care- 

 fully examined but no eggs in segmentation could be found, — whereas 

 fifteen separate experiments upon the ova of seventy-five individuals 

 never failed to give a larger or smaller per cent of fertilized ova, when 

 a number of spermatozoa had previously been added. • 



This, I think show^s clearly that the segmented ova were not pre- 

 viously fertilized internally, but that they were the products of an ex- 

 ternal, artificial fecundation. 



The ovaries of the larger specimens contained an enormous number 

 of ova, about ten per cent of which under the most favorable circum- 

 stances could be successfully impregnated. The ova thus artificially 

 impregnated underwent a normal development and after six days had 

 produced a provisional nautiloid shell. After twelve days (the longest 

 time I succeeded in keeping them alive) the larvae still swam about 

 and showed no signs of assuming the adult form. 



The same condition found in Patella, as regards absence of an 

 albuminous gland and external sexual organ, prevails in Haliotus and 

 Fissurella, and I believe that the ova of both these genera could also 

 be fecundated artificially, but unfortunately it did not occur to me to 

 try it until after the spawning season had passed 



3. Vorläufige Mittheilungen über Archenchytraeus Möbii n. sp. 



Von W. Michaelsen, Kiel. 



eingeg. 27. Januar 1885. 

 Ä. Möbii lebt in angeschwemmtem Seegras am Strande der Kieler 

 Bucht. Er ist 20 — 35mm lang, hat ungefähr 60 borstentragende Seg- 

 mente und ist milchig weiß. Die Borsten sind fast gerade mit schwach 



