244 



THE CEPHALOPHORA. 



§215. 



§ 215. 



With those Cephalophora which are nourished by solid food, and which 

 often have, therefore, masticatory organs, there are, almost without exception, 

 highly-developed Salivary organs. These are usually composed of two lob- 

 ular yellow glands surrounding the oesophagus or stomach, and which have 

 in front two excretory ducts which are lined with ciliated epithelium.''* 



These ducts pass, in company with the oesophagus, through the oesopha- 

 geal ring, and, extending over the base of the pharynx, end in the oral 

 cavity on each side of the tongue. With some species, these glands con- 

 sist of two very long tubes.'-' Some Gasteropoda have two pairs of these 

 organs, one of which opens at the anterior part of the mouth. '^' In a few 

 cases only these organs appear to be wholly wanting. <■*> 



The Biliary organs are always present ; and their glandular follicles con- 

 tain hepatic cells filled with a brownish-yellow substance.*''' Most com- 

 monly, the liver is large and distinctly separated from the digestive canal ; 

 and it is with a few genera only that it is more or less blended with it. 



1. This last is the case with some Pteropoda, and Apneusta, whose 

 intestinal walls, as with the Worms, are partly composed of the hepatic 

 substance, or furnished with numerous small follicles which open into the 

 intestinal cavity.'^' 



1 Helix, Umax, Onchidium, Haliotis, Pleu- 

 robranchus, and the Pectinibranchia. For the 

 internal structiu-e of these glands, nee Muller, De 

 Gland, secern, struct, p. 54, Tab. XVII.* 



2 Clio, Aplysia, Thetis, Lissosoma, Tergi- 

 pes, and many species of Doris. 



3 Jantliina, Flabellina, Actaeon, and Atlanta. 

 With some Gasteropoda, as for instance, with 

 Rhodope, and Kolidina, there are only two sali- 

 vary glands ; these open in front into the oral 

 cavity and so far from the oesophagus that they 

 appear to correspond to the anterior pair of tliose 

 species in which there are four, t 



4 Sagitta, Cymbulia, Tiedemannia, Denta- 

 lium, and Chiton. 



5 For the internal structure of the liver of the 

 Gasteropoda, see Muller, De Gland, secern. &c. 

 p. 71, Tab. X. ; Schlernm, Be hepate ac bile Crus- 

 tac. et Mollusc, ([uorundam, loc. cit. p. 19, Tab. I. 

 II. ; Karsten, iSiov. Act. Acad. Nat. Cur. XXI. 

 p. 304, Tab. XX I. ; and H. Meckel, Muller's 

 Arch. 1846, p. 9, Tab. I. + 



6 With Sagitta, tlie hepatic substance appears 



to be blended with the intestinal walls (Krohn, loc. 

 cit. p. 8). This is distinctly so with Venilia, Aeolis, 

 Eolidina, Amphorina, and Zephyrina, and is 

 especially seen upon the coecal ends of the 

 branches of the intestinal canal which terminate 

 partly in the dorsal appendages, and partly in the 

 parenchypia of the body ; see Quatrefages, loc. cit. 

 XIX. p. 289, PI. XI. fig. 5, I. PI. IV. V. ; Alder, 

 Hancock and Embleton, Ann. of Nat. Hist. XIII. 

 p. 163, PI. II. flg. 9, XV. p. 80, PI. IV. According to 

 Nordmann (loc. cit. p. 20, Tab. n. III. flg. 3), the 

 liver is isolated with Tergipes ; but as the organ 

 here described appears to open externally by a 

 special duct, it resembles an urinary organ (see 

 below, § 223). With Pneumodermon, and Clio, 

 the stomach is lined with a layer of small hepatic 

 folUcles {Cuvier, loc. cit. p. 8, fig. 7, p. ; and 

 Eschricht, loc. cit. p. 11). 



According to a communication from Kolliker, 

 the intestine of Rhodope also has numerous folli- 

 cles of this kind, which are pyriform and filled 

 with cells having yellow nuclei. 



* [§ 215, note 1.] gee also Leidy (loc. cit.) for 

 the salivary glands and their intimate structure, of 

 Limax, Helix, Tebennophorus, Vaginula, Suc- 

 cinea, Glandina. 



t [ § 215, note 3.] With Paludina, the salivary 

 glands are hi^^hly developed and two in number. 

 They are situated on the upper and posterior side 

 of the pharynx, behind the brain ; their excretory 

 ducts pass under the cerebral commissure, for- 

 wards, and perforate the ujjper wall of the pharynx. 

 In structure they consist of ramose caeca, made 

 up essentially of cylindrical epithelium situated on 

 a basement membrane ; see Leydig, loc. cit. p. 

 165, Taf. XII. fig. 10, a. b. 



For further details on these organs with the 

 Nudibranchiate Cephalophora in general, see 



Alder and Hancock, loc. cit. Part II. PI. IV. fig. 



I, f. (Doto); Part III. PI. VII. fig. 6, a. (Aeolis); 

 Part IV. PI. V. fig. 1, c. (Scyllaea) ; Part V. PI. 



II. fig. 1, h. (Doris). — Ed. 



X [ § 215, note 5.] See also Leydig, tieber Palu- 

 dina vivipara, kc, loc. cit. p. 143, 166 (Paludi- 

 na) ; he gives its development and its adult struc- 

 tm-e. It is developed from cells as an appendage 

 to the alimentary canal ; and its structure, when 

 complete, is follicular, as above described. See 

 furthermore, for the liver of the terrestrial Gaster- 

 opoda, Leidy, loc. cit. Of its internal structure. 

 he says : " The lobuli of the liver are composed of 

 the rounded commencement of the biliary ducts, 

 and are lined with polygonal cells." — Ed. 



