262 THE CEPHALOPHORA. §$ 228. 
form prolongation (Flagellum). In many of the genera of the Gastero- 
poda, the Vas deferens is inserted upon the penis near its hase, or at the 
posterior end of its cavity.* The penis has also inserted into it many 
small retractor muscles which arise from the walls of the envelope of the 
body, or on the columella. 
The external orifices of these hermaphroditic genital organs are usually 
on the right side, and present the following relations: 1. The vagina and 
penis open into a common genital cloaca which communicates externally 
upon the sides of the anterior part of the body. 2. The two orifices are 
situated side by side,— that of the penis directly in front of that of the 
vagina. 8, The orifices are quite removed from each other, and then the 
penis, which is usually concealed beneath the testicle of the right side, 
communicates with the genital cloaca situated behind, by a groove which 
runs along the sides of the body.“ This groove is lined with ciliated 
epithelium, and, without doubt, conducts the semen from the genital cloaca 
to the penis, during copulation. 
§ 228. 
The Cepbalophora with which the sexes are separate, may be divided into 
two sections, in one of which, the copulatory organs are wanting, while im 
the other, they are highly developed. 
1. To the first section, belong the Cyclobranchia, the Scutibranchia, 
and also, probably, the Tubulibranchia and Cirribranchia; with all of 
which, the genital glands are easily seen at the epoch of procreation, from 
the presence of sperm or of eggs. 
19 The penis is short, and of a compact, form 
with the Pteropoda; see the figures of that of 
Cymbulia, Tiedemannia, Hyalea, Cleodora, 
Cuvieria, and Limacina, in Van Beneden, 
Exerc. zoot. loc. cit. Clio, however, forms an 
exception in this respect, its penis being long and 
flexuous (Eschricht, loc. cit. Tab. III. fig. 24). 
With the Apneusta, this organ is pretty long, 
spiral-form, and concealed in a pyriform sac, and 
the Vas deferens is inserted at its base ; see Adl- 
man, loc. cit. Pl. VI. t. (Actaeon), and Nord- 
mann, loc. cit. Tab. III. fig. 5, p. q. r. (Tergipes). 
There is a similar disposition with Thetis, T'rz- 
tonia, Doris, and Pleurobranchaea (H. Meckel, 
loc. cit. Taf. XV.). In the last-mentioned genus, 
it is distinguished for its extraordinary length. 
That of Arion, Limax, Succinea, Lymnaeus, 
Planorbis, Physa, Clausilia, Helix cellaria, and 
Jruticum, is thick, very short, and unites either 
abruptly or gradually with the Vas deferens ; 
while that of Bulimus, and most species of Helix, 
ends posteriorly in a long lash which projects 
freely into the cavity of the body, and upon which 
is inserted the deferent canal at a variable distance 
from the extremity (Wohnlich, Treviranus, Erdl, 
Paasch, loc. cit.). With Onchidium, Bullaea, 
and Gasteropteron, the penis has a very long, 
flexuous lash, which, with Aplysia, and Pleuro- 
branchus, is shorter, but never in connection with 
the Vas deferens (Cuvier, and H. Meckel, loc. cit.). 
20 These retractor muscles are inserted at the 
posterior extremity of the penis with Arion, 
Limaz, and Planorbis ; and more in front and on 
the sides with Lymnaeus, and Helix (Wohnlich, 
Erul, and Paasch, loc. cit.). 
21 Such a common genital orifice is found with 
Heliz, Limaz, Arion, Succinea, Bulimus, and 
Clausilia, on the right side of the neck behind the 
tentaclea ; it is situate1 further behind, but always 
on the right side, with Aolis, Tergipes, Scyllaea, 
Doris, Tritonia, Thetis, Pleurobranchus, Pleu- 
robranchaea, and Diphyllidia. 
22 With Planorbis, and Physa, the male and 
female orifices are situated on the left side of the 
neck behind the tentacle ; with Flabedlina, Rho- 
dope, Cleodora, and Cuviera, a little further be- 
hind on the right side. 
23 With most of the Pteropoda (Clio, Cymbulia, 
Tiedemannia, Hyalea, and Limacina), the orifice 
of the penis is in the neck, and that of the genital 
cloaca a little further behind on the right side. 
With Actaeon, and Lissosoma, the two orifices 
are also on the right side, but even more widely 
separated from each other. With Gasteropteron, 
Bulla, Bullaea, and Aplysia, the genital cloaca 
is very far behind, while the penis is under the 
right tentacle. With Doridium, the cloaca is also 
quite in the rear, but upon the left side, and con- 
sequently the penis is under the tentacle of the 
same side. But with Onchidium, these orifices 
are the widest apart, — the cloaca opening close by 
the anus, and the penis under the right tentacle. 
The furrow passing from the cloaca to the penis is. 
found with all these Gasteropoda, and it is very 
probable that it will be found also with all the 
other Cephalophora, whose penis is entirely re- 
moved from the other male genital organs. 
The furrow which Van Beneden (Exerc. zoot. 
Fasc. II. p. 46) observed with a Hyalea, between 
the two genital orifices, shows that there is such a. 
communication with the Pteropoda also. 
1 The separation of the sexes with Chiton, Patella, 
and Haliotis, was first shown by R. Wagner and. 
Erdl (Froriep’s neue Notiz. No. 249, 1839, p. 102). 
It has been confirmed with Patella, by Milne 
Edwards (Ann. d. Sc. Nat. XIII. 1840, p. 376), 
and by Robin and Lebert (Ibid. V. 1846, p. 191). 
With many individuals of Vermetus gigas, I have 
