^ 225. 



THE CEPHALOPHORA. 



255 



2. The genus Aplysia has an apparatus of particular secretion, consisting 

 of a group of pyriform follicles situated under the branchia, inside of the 

 skin. Its excretory orifice is behind the female genital opening, and its 

 secretion is a whitish li(|uid with attributive corrosive qualities.^'" 



3. Many of the Pectiuibranchia, and Tubulibranchia, have upon the 

 upper wall of the cavity of the mantle, a row of folds which secrete an 

 extraordinary quantity of viscous mucus which is not excreted through any 

 particular duct.'"^* 



4. With several terrestrial Gasteropoda, the median line of the foot is 

 occupied by a straight canal lined with ciliated epithelium, which ends in 

 a large orifice situated under the mouth. On each side of this canal, are 

 rows of follicles that secrete a granular mucus which, passing into its cav- 

 ity, is excreted externally, probably by means of cilia.*"' 



CHAPTER IX. 



ORGANS OF 0ENERATION, 



§ 225. 



The Cephalophora propagate solely by means of male and female genital 



by a narrow canal, with the prolongations of the 

 digestive cavity which enter into the dorsal ap- 

 pendages, and their contained liquid is subjected to 

 a process of respiration. But Nordmann (loc.cit. 

 p. 33, Tab. II. R. R.) has been unable to find any 

 such communication between these two organs, 

 with Tergipes, and he has distinctly seen the 

 granular mucus which is expelled from the follicles 

 from contraction, escape through an orifice on the 

 extremity of each dorsal appendage. Vi'MxAeolis, 

 according to Hancock and Embleton (loc. cit. p. 

 SO, PI. IV. v.), the product of these follicles is quite 

 interesting. It contains elliptical vesicles which im- 

 mediately burst when put in water, exposing a 

 transparent cylinder, out of which a filament, 

 sometimes of a spiral form, is projected as swift as 

 lightning. They compared these bodies to sperm- 

 atic particles ; but to rae, the.v appear exactly like 

 the nettling organs of Actinia. Hancock and 

 Embleton have also seen and figured with Aeolis, 

 a canal of communication between these follicles 

 and the prolongations of the digestive canal, but it 

 may be questioned if this was not an artificial 

 formation produced by compression of these organs 

 during the examination.* 



•4 See Cuvier, loc. cit. p. 4, fig. 2, S. ; Delle 

 Ckiaje, Meraor. II. p. 56, Tav. II. fig. 2, 0. fig. 

 3 ; and Rang, Ilist. Nat. des Aplysies, p. 26. 



•i These muciparous organs described by Cuvier, 

 with Buccinum (Mem. loc. cit. p. 6, fig. 3, f.) as 



* [ § 221, note 3.] See for further description, 

 together with figures of these peculiar bodies con- 

 taining a spiral thread, Alder an<I Hancock, loc. 

 cit. Part III. PI. VIII. fig. 14 (Aeolis) ; they correct 

 their former view (mentioned above) and admit, 

 what I thiuk is not in the least doubtful, Uiat tliey 



Feuillets muquevx, are also found with Mures 

 (Ei/.ienhardt, in MeckeCs Dcutsch. Arch. VIII. 

 p. 215, Taf. III. m. m.), Terebra, Turbo, Valuta, 

 Cypraea, Harpa, Do/ium, Cassia, Tritonium, 

 &c. {Qiioy and Gaimnrd, Voy. do I'AstroIabe, loc. 

 cit., or Isis. 1S36, p. 35, Taf. II. fig. 6, (|. Taf. III. 

 fig. 10, X. 18, m.). Carus (Museum Senckenberg. 

 II. 197, Taf. XII. fig. y, h.) has seen similar mu- 

 cous fohls viWhMagilus. With Fermetus, on the 

 contrary, I have found only a single, Itut a very 

 considerable, longitudinal fold which runs along 

 by the side of the rectum and covers the excre- 

 tory duct of the genital organs. 



6 This muciparous apparatus of Bulimus, He- 

 lix, Limax, and Arion, was announced in 1829, 

 by Kleeberg, at the Congress of Naturalists at 

 Heidelberg (Isis, 1830, p. 574) ; but it had not es- 

 caped the observation of Delle Chiaje with many 

 Helicina and Limacina (Descriz. II. p. 10, Tav. 

 XXXVII. fig. 17, X.). It is therefore surprising 

 that it remained thus long unknown to other natu- 

 ralists. The assertion of Kleeberg, that with Li- 

 max, and Arion, the mucous canal communicates 

 with the venous system, I have been unable to con- 

 firm by observations upon Arion. Leydig de- 

 clares that this mucous canal with the terrestrial 

 Gasteropoda is the seat of the sense of smell ; see 

 Schleiden and Froriep's Notiz. IV. p. 24, or Ann. 

 of Nat. Hist. XX. p. 210. 



are analogous to the nettling organs of the Polyps. 

 Agassiz has carefully observed them, and they 

 have all the characteristics of a true lasso-cell ; to 

 this I may add ray own observations upon other 

 Mollusca. — Ed. 



