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 base, 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 envelo^je 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. '^-^ 3. 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 Cephalophora with which the sexes are separate, may be divided into 

 two sections, in one of which, the copulatory organs are wanting, while in 

 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 f^an Beneden, 

 Exerc. zoot. loc. cit. Clio, however, forms an 

 exception in this respect, its penis being long and 

 flexuous (Eschricht, loo. cit. Tab. III. fig. 24). 

 With the Apneusta, tiiis organ is pretty long, 

 spiral-form, and concealed in a pyriform sac, and 

 the Vas deferens is inserted at its base ; see All- 

 man, loc. cit. PI. VI. t. (Actaeon), and Nord- 

 mann, loc. cit. Tab. III. fig. 5, p. q. r. {Tergipes). 

 There is a similar disposition with Thetis, Tri- 

 tonia, Doris, and Pleurobranchaea (H. Meckel, 

 loc. cit. Taf. XV.). la the last-mentioned genus, 

 it is distinguished for its extraordinary length. 

 That of Arion, Limax, Succinea, Lyrnnaeus, 

 Planorbis, P/ii/sa, Clausilia, Helix cellaria, and 

 fruticum, 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 {iVohnlich, Treviranus, Erdl, 

 Paasch, Inc. cit.). With Onchidium, Bu/laea, 

 and Gasteropteron, the penis has a very long, 

 flexuous lash, which, with Aplysia, and Pletiro- 

 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, 

 Limax, and Planorbis ; and more in front and on 

 the sides with Lyrnnaeus, and Helix (^If'ohnlich, 

 Erdl, and Paasch, \oc. cit.). 



m Such a common genital orifice is found with 

 Helix, Limax, Arion, Succinea, Bulimus, and 

 Clausilia, on the right side of the neck bi'hind the 

 tentacles ; it is situate! further behind, but always 



on the right side, with Molis, 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 Flabellina, Rho- 

 dope, Cleodora, and Cuviera, a little further be- 

 hind on the right side. 



'£i With most of the Pteropoda (C/!0, CymBu/ia, 

 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 i.4 

 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. 

 Tasc. 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. fVagner 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. 37ü), 

 and by Robin and Lebert (Ibid. V. 1846, p. 191). 

 With many individuals of Vermetus gigas, I have 



