354 Prof. E. Claparede on the Structure of the Annelida. 



branchi, which will be described in the special portion of the 

 present memoir. The formation of the ova in the Terehellea 

 and Serpulea departs from it still more widely ; but throughout 

 we shall find a cellular tissue, either fixed or composed of float- 

 ing elements, in the midst of which the sexual elements are 

 developed. 



The sexual glands have indeed been known for a long time in 

 certain Annelida ; but these early observations have been in part 

 forgotten. Thus whilst Pallas* erroneously represented the ova 

 of Aphrodita as originating in the liquid of the perivisceral 

 cavity, G. R. Treviranusf and Delle Chiaje J were well acquainted 

 with the true ovaries at the base of the feet in these worms. 

 Delle Chiaje also indicates the ovaries of the Pherusea, Her- 

 mione, Polyodonta, Parthenopeia, Diupjatra, Nephthys, Telamon, 

 &c. He knew very well that the ova are formed in the ovaries, 

 but that, when arrived at maturity, they detach themselves 

 therefrom, and float freely in the perivisceral cavity §. Even 

 the existence of a blood-vessel in the axis of the sexual glands 

 was not; unknown to some observers. Thus Delle Chiaje || indi- 

 cates the axial vessels of the ovarian racemes in Siphonostomum 

 and the Stylaridida ; M. Stannius^ has made analogous obser- 

 vations on Arnphinome rostrata ; M. Grube has seen the ovules 

 originate round vessels in the Arenicola;^^; and M. Schmardaff 

 describes the axial vessel in the ovaries of Euphrosyne. All these 

 observations appear to have met with little credit, but they are 

 none the less perfectly correct. 



Frequently, it is true, organs have been wrongly regarded as 

 sexual glands. For example, wherever Rathke believed he saw 

 testes in the Nereides, Pectinaria, &c. he was mistaken J J. All 

 authors have been mistaken with regard to the testes of the 

 Arenicolce. The segmental organs of the Terehellea have also 

 had the fate of being taken for ovaries by nearly everybody from 

 Cuvier to MM. Milne-Edwards, Grube, Quatrefages, and even 

 Sars. Dr. Williams, of course, did not remain behind, as this 



* Miscellanea Zoolo2;ica, p. 91. 



t Zeitschrift fur Physiol. Bd. iii. p. IfiS. Darmstadt, 1829. 



\ Descrizione e Notomia, &c. torn. v. p. 59. 



§ Istituzioni di Anat. Comp. ed. 2. torn. ii. p. 158. 



II Descrizione, &c. torn. iii. p. l'^- 



IT Isis, 1831, pp. 989-990. 



** Ziir Anatomic der Kiemenwiirmer, 1838, p. 16. 



tt Nene wirbellose Tliiere, Bd. ii. p. 137. 



\X Rathke himself, however, recognized these errors as soon as he 

 perceived that the Arenicolce, the Ammotrypance , &c. had the sexes sepa- 

 rate. The segmental organs, which he had previously regarded as testes, 

 then became to him muciparous glands. (See " Beitrage zur Fauna Nor- 

 wegens," Nova Acta, &c. 1843, tom. xx. p. 201.) 



