216 THE ACEPHALA. $ 198. 
that of the parent, and the envelope of the mantle alone is common to 
both.” 
§ 198. 
With the Acephala, the sexes are sometimes separate, sometimes united’ 
jn one individual. But the genital organs are very fully developed, and, 
as with the Zoophytes, consist of an ovary and a testicle with an excretory 
duct; but in none are there copulatory organs, or uterine reservoirs for the 
eggs, 
othe eggs are usually spherical, rarely pyriform or elliptical. The pale 
yellow or reddish vitellus is finely granular, and surrounded with a vitel- 
line membrane and a smooth colorless chorion. 
The germinative. vesicle has usually two nucleoli cemented together. 
Often there is a layer of white substance interposed between the chorion 
and the vitelline membrane.” 
The sperm is milky, and, at the epoch of procreation, quite full of very 
active spermatic particles. These always consist of an oblong, oval, or 
pyriform body, to which is abruptly attached a delicate tail, whose motions 
are not affected by the water in which these animals live.” 
With the Acephala of separate sexes, the ovaries and testicles so closely 
resemble each other, not only as to their form and the arrangement of 
excretory ducts, but also as to their locality in the body, that they are 
with difficulty distinguished each from the other, except at the period of 
procreation. 
The copulatory organs being absent, here, as with the Zoophytes, the 
water is the fecundating medium. 
1 This multiplication by buds has been observed 
‘by Milne Edwards with Botryllus, Polyclinum, 
Amaroucium, Didemnum, and Perophora. | It 
occurs also, undoubtedly, with other compound 
Ascidiae, and is the cause of the increase of the 
Ascidian-stock with the colonies of these animals. 
With the simple Ascidiae— Clavelina lepadifor- 
mis, and producta, the buds take the form of 
suckers (Stolones), and the new individuals are 
separated from their parents with the separation of 
the mantle ; see Milne Edwards, Sur les Ascidies 
composées, loc. cit. p. 41, Pl. ILI. fig. 2°. (Ama- 
roucium proliferum), Pl. VII. 1, 1». le. (Bo- 
trylloides rotifera), and Pi. II. fig. 1°. 38 (Clav- 
elina), Eysenhardt (Nov. Act. Acad. Leop. Carol. 
XI. p. 263, Tab. XXXVI. fig. 1, &c.), has also ob- 
served these stolons upon a simple Ascidian. 
1 These eggs have been figured by Wagner, Pro- 
4dromus, &c., p. 7, Tab. I. fig 5; Carus, Erliuter- 
ungstafeln, &c., Hft. V. Taf. 1, fig. 2,and Nov. Act. 
Acad. Leop. Carol. loc, cit. p. 26, Tab. I. (Ano- 
donta and Unio), and by Milne Edwards, Sur les 
Ascid. comp. p. 26, PL. IV. fig. 1-3 (Amaroucium). 
* [§ 198, note 2.] The spermatic particles of 
the Acephala throughout, are according to my own 
observation, of a Cercaria-like form, — that is, hav- 
ing a distinct head to which is attached a more or 
Jess delicate tail. Their development, which I 
have traced in many cases, is in special, daughter- 
cells as with all other animals. They may, as 
indeed they ofteu do, assume various groupings 
afterwards, but the real development appears sim- 
ple and invariable. The shape of the head of the 
2 The spermatic particles of the Acephala have 
been described and figured by Wagner, in Wieg- 
mann’s Arch. 1835, II. p. 218, Taf. III. fig. 8 
(Cyclas); Siebold, in Miller’s Arch. 1837, p. 
381, Taf. XX. fig. 12-14 (Unio, Anodonta, My- 
tilus, Tichogonia, Cardium, Tellina, Mya and 
Cyclas); Kolliker, Beitrage, loc. cit. p.37 (Pho- 
las), and Krohn, in Froriep’s neue Not. No. 356, 
p. 49, 52 (Phallusia and Salpa). Those of Ama- 
roucium described by Milne Edwards (loc. cit. p. 
21, Pl. III. fig. 1¢.) differ from the usual type in 
being fusiform and very long, — their tail not being 
distinct from the body. Those of a Cynthia have 
appeared to me of a similar form, — only the tail 
was much longer and more delicate. With Phai- 
lusia, on the contrary, I have distinctly seen them, 
with an oblong body to which is abruptly attached 
the tail. The sperm of Polyclinum, Botryllus, 
Didemnum, Diazona, and Phallusia, contains 
spermatic particles of a Cercaria-form ; while those 
of Salpa are filamentoid; see Kélliker, Neue 
schweiz. Denkschr. VIII. p. 43, fig. 30, 49, 58-57.* 
particle I have found to differ widely, yet in each 
case to present an uniformity of a zoological value, 
Sometimes it is perfectly globular (Polyclinum), 
sometimes oval (Unio, Anodonta), sometimes ovo- 
globular (Ostrea), sometimes oblong (Ascidia), 
sometimes pyriform (Mytilus), sometimes conico- 
pyriform (Mya), and sometimes long-conical (Cy . 
prina). These forms may seem a refinement more 
ideal than real, but the exact forms are determined 
by micrometrical measurements. — Ep. 
