562 



ME. H. RIDLEY ON THE 



The alimentary tract, the vascular system, the nephridia, all 

 exhibit the characters peculiar to or present in Urochceta. 



There is but a single pair of seminal reservoirs, which have a 

 greater extent than in JJ. coretlirura (F. Mliller *) ; for in the 

 present specimen that lying on the left side passes through eight 

 somites, that of the right side passes through twelve somites, 

 coramenciug in somite xir., where are situated also the ciliated 

 rosettes. 



I was unable to trace the sperm-ducts ; I could find no ovary ; 

 I did not look for testes, as this would have necessitated some 

 damage to the worm, which I was anxious to injure as little as 

 possible. 



There are three pairs of spermathecse ; each is a very elongate, 

 thin- walled sac, enlarged distally, and lying respectively in somites 



VII. , VIII., IX. The chief diff'erence between the two species of 

 UrochfRta that have received names lies in the different position 

 of the spermathecse. In Z7. coretlirura they lie in somites 



VIII. , IX., X.; in V . dubia (Horst) they are fouud in somites 

 VI., VII., VIII. ; in Beddard's specimen from Australia they 

 have the same position as in the present specimen. 



Such is a brief sketch of the anatomy of the worm A, from 

 Fernando INoronha; it is sufficient, however, to identify it' as 

 belonging to the genus UrochcEta ; but as to the species — 

 whether it belongs to any of those already described or 

 requires a new name — I feel rather diffident of expressing an 

 opinion. In most points it agrees closely with U. coretlirura ; 

 but in the position of the gizzard (in somite vi. instead of vii.), 

 in the position of the spermathecae, and in the fact that the setae 

 are not bifid, the two forms differ. On this last point I think no 

 great stress can be laid, as Beddard recognizes no bifidity in 

 hia Australian specimen ; and I agree with him so far as the 

 present specimen is concerned, which differs also from Horst's 

 species, JJ. duhia, in the position of the spermathecse ; in 

 fact, with regard to these organs, the present and Beddard's 

 specimen are intermediate between Horst's and Perrier's 

 species. But are we justified in establishing a new species on 

 such slender grounds, and from an examination of a single speci- 

 men ? I think not, and prefer to leave the specimen unnimed, 

 and to regard it as belonging to Perrier's species, of which it 

 may be a variety ; for we are at present ignorant as to how far 

 * See Perrier, Arch. d. Zool. exper. et gen. iii. 1874. 



