182 THE ANNELIDES. $ 169. 
tween the feet of many Branchiati, serve for the escape of the sperm and 
eggs. With others, the cavity of the body opens outwardly, probably by 
a loss of the last.segment, especially with those which are viviparous, 
The water is undoubtedly the medium of fecundation, and receives the 
sperm from the males, probably through orifices like those which serve for 
the escape of eggs with the female. 
With the viviparous Branchiati, water filled with sperm can enter the 
body and fecundate the eggs through these same openings. 
§ 169. 
The development of the Annelides as far as yet known, occurs after two 
different types; but it always commences with a-complete segmentation of 
the vitellus.: ; : 
I; With the Hirudinei, after the vitellus has divided into many large 
cells, a central one becomes distinguished from the others by its still further 
division; this becomes the digestive tube. The others, still dividing, form 
a primitive embryonic part in which appears the future ventral and nervous 
ortion. j : 
’ The embryo is at first spherical, and ultimately is covered with a delicate 
ciliary ‘epithelium. A kind of sucker is then developed upon a certain 
point of its surface; this connects with the stomach, and through it is re- 
ceived, for food, the albumen surrounding the embryo. It then gradually 
lengthens, and, losing its ciliary epithelium before the escape from the egg, 
a sucker appears upon the posterior extremity, and it finally becomes 
fully developed without a Metamorphosis.® 
II, With the Branchiati, there is a complete metamorphosis. The seg- 
mentation of the vitellus is uniform throughout, and this last is finally 
changed into a round embryo — which, escaping from the egg, swims freely 
about like an Infusorium, by means of the ciliated epithelium which covers 
its whole body. ‘The embryo then lengthens, and the epithelium disappears 
4 According to Milne Edwards’ observations 
upon several Capitibranchiati, as T'erebella, Ser- 
pula, Protula, &c., the eggs are glued together in 
roasses by an albuminous substance, and attached 
to the stones of the anterior border of their cases ; 
see Ann. d. Sc. Nat, III. 1845, p. 148, 161, Pl. V. 
fig. 1, Pl. VII. fig. 28, PI. IX. fig. 42. With Poly- 
noé cirrata, on the other hand, masses of eggs are 
attached and borne about on the scales of their 
body ; see Sars, in Wiegmann’s Arch. 1845, I. p. 
18, Taf. I. fig..12. With the females of Exogone 
and Cystonereis, the eggs are situated in longi- 
tudinal rows upon the ventral surface ; see Orsted, 
in Wiegmann’s Arch. 1845, I. p. 21, Taf. IL. fig. 
4, and Kélliker, in an as yet unpublished memoir 
for the Helvetic Society, titled: Einige Worte zur 
Entwickelungsgeschichte von Eunice, von H. Koch 
in Trieste, mit einem Nachwort von Kélliker. 
[Additional note.] The often-quoted memoir of 
Koch and Kélliker on the development of the An- 
* [§ 168, note 4.] According to Felix Dujar- 
din (Ann. d. Sc. Nat. XV. 1851, p. 298) Exogone 
pusilla is androgynous. Beside the well-known 
pediculated ovarian sacs on the ventral surface, 
each segment of the body, except the first two, 
has, with this species, a dorsal, fusiform cirrus, in 
which are developed spermatic particles. This ob- 
nelides has recently appeared in the Neue Schweiz. 
Denkschr. VIII.* 
5 According to my friend H. Koch of Trieste (in 
the MS. just indicated), the eggs of a species allied 
to Eunice sanguinea, are developed in the cavity 
of the female body, whence the young escape 
through a rupture of its posterior extremity. 
1 See F. de Filippi, Lettera sopra ]’Anatomia, e 
lo sviluppo delle Clepsine, Pavia, 1839, Tav. II. ; 
Grube, Untersuch. tiber die Entwick. d. Clepsine, 
p. 15, Taf. L., and Frey, Zur Entwickel. von. Nephe- 
lis vulgaris, in Froriep’s neue Not. No. 807, 
1846, p. 228. The old observations of E. H. We- 
ber (Meckel’s Arch. 1828, p. 366, Taf. X. XI.) 
and R. Wagner (Isis, 1832, p. 398, Taf. IV.) agree: 
very well with those of Filippi 
As yet, we possess nothing upon the develop- 
ment of Lumbricini, whose young, as is known, like 
those of the Hirudinei, leave their cocoons without 
undergoing any metamorphosis.t 
servation, from its singularity, requires confirm- 
ation. — Ep. 
+ [§ 169, note 1.] For the embryology of Ne- 
mertes, see Desor, Boston Jour. Nat. Hist. VI. p. 
1. The general facts accord with those mentioned 
in the text. — Ep. 
