354 Prof. E. Claparéde 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 Terebellea 
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. Treviranust and Delle Chiajet 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, Divpatra, 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 Stylariotda ; M. Stannius { has made analogous obser- 
vations on Amphinome rostrata; M.Grube has seen the ovules 
originate round vessels in the Arenicole**; and M. Schmardat+t 
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 mistakenf{. All 
authors have been mistaken with regard to the testes of the 
Arenicole. The segmental organs of the Terebellea 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 Zoologica, p. 91. 
+ Zeitschrift fir Physiol. Bd. ii. p. 165. Darmstadt, 1829. 
+ Descrizione e Notomia, &c. tom. v. p. 59. 
§ Istituzioni di Anat. Comp. ed. 2. tom. ii. p. 158. 
|| Deserizione, &e. tom. iii. p. 78. 
q Isis, 1831, pp. 989-990. 
** Zur Anatomie der Kiemenwiirmer, 1838, p. 16. 
++ Neue wirbellose Thiere, Bd. ii. p. 137. 
tt Rathke himself, however, recognized these errors as soon as he. 
perceived that the Arenicole, the Ammotrypane, &c. had the sexes sepa- 
rate. The segmentai 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.) 
