Affinities of the Onchidia. 265 



loped Inter bj invagination upon the alrea ly-fonned ophthal- 

 mophore (Eisig, Fol), it is certainly not of tlie importance 

 wliicli Brock would attach to this circuuistance. 



The relations of the pedal gland in the Onchidia are very 

 much as in the Stjlommatophora. While in some species 

 {0. tuniidumj Semper) this gland remains entirely, or for the 

 most part, enclosed in the foot, as in Philomycus"' ^ in most it 

 projects with its posterior part more or less into the body- 

 cavity f. The gland is much more strongly developed and 

 freer in position in Liniax inargijiatus, Drap4, iu Janella^j 

 and Limax j^&ctinatasW^ but especially in Triboaiophoras^. 



The digestive system of the Onchidia (including the liver) 

 shows hardly any important difference from that of the 

 Stylommatophora. 



The Onchidia are certainly " Opisthobranchiate," but so 

 also are the Veronicelke^ nay even ArionawiX Liniax^'^, all of 

 which, however, are undoubted Pulmonata. This position of 

 the heart is consequently here of no systematic signiticance, 

 especially as there are Opisthobranchiata which are proso- 

 branchiate [Acera, Gasteropteron) . 



The kidney of the Onchidia is parenchymatous, which is 

 never the case in the Nudibranchs ; it is for the most part 

 enclosed by the substance of the lung, or at least reaches the 

 Avail of the pulmonary cavity only at a i^w ]joints. Jts cha- 

 racter again is essentially as in the Pulmonata, only the 

 neighbouring pulnionary cavity is much smaller because the 

 respiration is to a great extent cutaneous. Joyeux-LafFuie 

 denies to 0. celticum any real lung-substance, and represents 

 the organ in question as consisting exclusively of renal tissue ; 

 but this assertion is scarcely correct, and will hardly be con- 

 firmed by later investigations. The organ of communication 

 between the pericardium and the renal cavity ("Nieren- 

 spritze " of Bergh), which always occurs in the Nudibran- 

 chiata, has been of late years recognized by Semper ff and 



* R. Bargh, " Untersuchimgeu cles Triboniophorus Sehulteii, K.," 

 Verhandl. li.-k. zool.-bot. Ges. in Wien, Bd. xx. (1870), pp. 860, 865. 



t Kei'ersteiiJ, " Zur Auatooiie von Phihmycus carolinensis" Zeitschr. 

 f. wiss. Zoo'. Bd. xvi. (1866), p. 187, pi. ix. tig. iJ,///^ ; R. Bergli, ' Chal- 

 lenger ' Expedition, /. c. pi. vii. fig. 1. 



I Zeitsclir. 1". wiss. Zool. Bd. viii. (1857), p. 351 (Semper). 



§ Kelerstein, " Ueber die Auatomie der Jimella bitentaculata,' Zeitschr. 

 f. wiss. Zool. Bd. XV. (1865), p. 449, pi. xsxiv. tig. 3, (/p. 



II Malakolog. Blatter, 1865, p. 107, pi. ii. fig. S, c/p. 



^ Keferstein, " Ueber die zweitentakeligen Landschnecken," Zeitsclir. 

 f. wiss. Zool. Bd. XV. (1864J, p. 84, pi. vl. tig. 4, rp}. ; Bergh, /. c. (1870), 

 p. 860. 



** See Iliering, ' Nervensystem,' &c. 1877, p. 226. 



ft Semper, I. c. (1877), p. 485, note 1. 



