290 



species we have a precisely similar alternation in the position of the 

 apertures of the nephridia as has been recorded by Per rie r in Plx- 

 tellus, but the copulatory pouches as well as the vasa deferentia open 

 by the ventral pair of setae while the nephridia of the same segments 

 open in front of the dorsal pair; this is the case at any rate with some 

 individuals: in others apparently belonging to the same species — distin- 

 guishable by no anatomical character from it — the nephridia open by 

 the same series of setae as the vasa deferentia. Moreover there is not 

 an absolute symmetry in the nephridia; the nephridia of opposite sides 

 of the same segment do not invariably open on to the exterior by the 

 same roAv of setae ; in some of the segments also there is not a regular 

 alternation in the position of the nephridia: the first five or six pairs 

 all open by the dorsal pair of setae; and in other regionsof the body there 

 are occasionally two or even three pairs of nephridia in as many con- 

 secutive segments opening by the same (usually the dorsal pair of 

 setae. The fact however which I especially Avish to record in the pre- 

 sent note is that it is possible to distinguish by certain ana- 

 tomical differences the dorsal from the ventral series of 

 nephridia; the former consist of a convuluted glandular tube connec- 

 ted with the exterior by a large thin walled muscular sac ; this sac no 

 doubt represents the muscular portion of the nephridium figured by 

 Gegenbaur in Lumbricus but is immensely larger: just at the point 

 where it pierces the body wall to reach the exterior it gives off a short 

 diverticulum prolonged beyond (above) the level of the setae in the same 

 straight line li. e.: transverse to the longitudinal axis of the body); in the 

 most anterior nephridia this coecal diverticulum disappears; the ven- 

 tral series differ in that the coiled glandular portion of the nephridium 

 opens near to the external aperture of a long oval muscular sac which 

 is thus a diverticulum of it. 



2. Remarques relatives aux recherches de Mr. Vigelius sur des 



Bryozoaires. 



Par A. Ostrooumoff. 



eingeg. 4. März 1855. 

 Grace à l'amabilité du respectable professeur S al en sky, j'eus 

 l'occasion de connaître le travail de Mr. ^ igelius: Die Bryozoen. 

 gesammelt während der dritten und vierten Polarfahrt des »Willem 

 Barents« in den Jahren 1880 und 1881 (Amsterdam, 1884). Les résul- 

 tats des recherches de Mr. Vigolius mêlaient connus en partie 

 d'après sa communication préliminaire insérée dans le No. 23 (I884i du 



