610 ox THE SEGMENTAL ORGANS OF APHEODITA, 



and by degrees, by the simultaneous growth of the Bryozoon and 

 the Sea- Anemone, such a complex organism as I have described 

 is produced. 



KoTE ON THE Segmental Organs of Aplirodita. 



By William A. Haswell, M.A., B.Sc. 



Having recently, for the first time had the opportunity of 

 ■examining specimens of Aphrodlta in the living state, I have been 

 able to study the structure of the segmental organs, which I find 

 to differ in no essential point from those of Pohjnoe as lately 

 described by me.* I have it on the authority of Pagenstecher,t 

 that the external apertures of these organs in Aplirodlta were 

 known to Treviranus. They have probably been noticed by 

 numerous observers since,! ^^^^ ^^^ tvMC arrangement of the 

 organs themselves seems never to have been made out,§ and 

 €ntirely erroneous descriptions of them have, as I have previously 

 had occasion to notice, been published and accepted. The external 

 apertures are situated, as in Polyno'e, on the ventral surface close 

 to the bases of the parapodia ; but there is no perforated tubercle 

 or cirrus as in the latter genus. The segmental organs themselves 

 consist of small, flattened, somewhat sigmoid, reddish-yellow sacs, 

 situated in contact with the ventral wall of the body a little 



* Proc. Linn. Soc, N.S.W., vol. vii., p. 262^ and ' Zoologischer Anzeiger,' 

 1882. 



t Allgemeine Zoologie, Theil iv. 



X Quatrefages among the number — He says (Hist. Nat. des Anneles, I., 

 p. 109) " Chez une Aphrodite hispide male, j'ai vu le sperme sortir, sons la 

 forme d'un filet blanc, de la base de la rame inferieure d'un seul cote 

 du dix-neuvieme anneau." 



§ Cosmovici in a paper on the segmental organs of Annelides publishel 

 jn the 'Archives de Zoologie Exfedmentale et Generale* whijh I have 

 not sean, has (as I learn from an abstract in the Journ. K.. Micro. Soc, vol. 

 iii., pp. 635 and 949.) described the segmental organs of the allied geniis' 

 Hermione. 



