SOME POINTS IN THE ANATOMY OP POLYCH^TA. 241 



literature of the subject with which it professes to deal, and 

 regard it as of merely psychological interest ; but the paper 

 contains detailed descriptions and drawings of the anatomy of 

 several forms of Polychseta, and these have been by some later 

 writers accepted as trustworthy. In a critical paper by R. S. 

 Bergh, 1 published in 1885 which reviews the relations of the 

 nephridia in the various classes of Vermes, the facts concerning 

 the Polychseta are mostly taken from Cosmovici's memoir. 

 But a great many of Cosmovici's statements are quite erro- 

 neous, and although he has described other facts correctly the 

 false is so mingled with the true, and the actual descriptions of 

 structure are so mingled with false theoretical views, that it is 

 not safe to accept anything in his paper without re-examination 

 of every case. 



Arenicola marina, Linnaeus. 

 In 1868, when Claparede's ' Chetopodes du Golfe de Naples' 

 was published the gonads of Arenicola were unknown. In that 

 work it is stated that most authors had taken the nephridia to 

 be reproductive organs, some describing them as ovaries, others 

 as testes. Quatrefages (' Hist. Nat. des Anneles,' 1865) called 

 the nephridia simply genital organs. Grube (' Zur. Auat. u. 

 Phys. der Kiemenwurmer') had assured himself that the ova- 

 ries were not to be sought in these organs, for he had seen (as 

 he thought) the ova formed on the exterior of vascular cseca 

 of the lining of the ccelom. He was inclined to regard the 

 nephridia as testicles. This was an impossible view, because, 

 as Claparede says, the sexes of Arenicola are separate, but it 

 seemed very probable to Claparede that Grube was right as to 

 the origin of ova, and in support of the opinion of Grube he 

 gives a figure of one of the ceecal pseudhaemal vessels surrounded 

 by a layer of cells. Claparede then quits the question of the 

 genital organs, and proceeds to give a not very accurate de- 

 scription of the nephridia in Arenicola Grubii, Clap. He 

 says the organs previously described as generative organs are 

 really segmental organs of a very peculiar structure, and are 

 1 ' Die Exkretions-orgaue der Wiirmer Kormes,' Bd. ii, 1S85. 



