Affinities of the Onchidia. 261 



small and half-concealed (Parinacella) or quite internal 

 (Liinax). Even within the dilFerent groups of the Styloui- 

 niatophora naked and shelled forms occur side by side, as 

 Liinax and VitrinUj Arioii and Helix *. And now, since a 

 shell has been demonstrated in the larva of Onchidium^ that 

 difficulty no longer exists. 



Thus, in a monographic memoir bj Jojeux-LafFuie f, the 

 developmental history has recently been described, not indeed 

 of a typical Oacliidium^ but of Otichidiam celticum. From 

 the author's description it appears clearly that the animal, as 

 a larva, possesses a shell, which is after^vards cast off. As 

 regards the other anatomical characters of the animal, Joyeux- 

 Laifuie especially points out that Onchidium " possesses no 

 organ representing the pulmonary or branchial cavity ; " the 

 so-called lung is only the cavity of the true kidney, the vas- 

 cular system of which is also inserted into the venous circu- 

 lation in the manner characteristic of the MoUusca generally ; 

 but nevertheless the organ does function as a lung \. At the 

 same time, however, he represents as the most essential the 

 respiration by means of the papillte of the skin (which are 

 branched in many Onchidia '\_Peronia~\)j and has also demon- 

 strated in them a strong vascular developuieut § (as already 

 asserted by Ihering in opposition to Semper) ; and, moreover, 

 he has experimentally proved the predominant importance of 

 this cutaneous or branchial respiration ||. Joyeux-Latfuie 

 further indicates the agreement of the Onchidia and the Pul- 

 monata in the structure of the nervous system and of the 

 digestive organs, and on the whole regards the Onchidia as 

 " marine branchiferous MoUusca witii a tendency towards 

 pulmonary respiration and a terrestrial existence." It is 

 therefore essentially rather upon physiological than morpho- 

 logical grounds that the author nevertheless places the animals 

 with the Pulmonata, at the same time referring to Corel's 

 well-known observations upon the Lynxniece of the Lake of 

 Geneva (L. ahyssicola). 



Of Joyeux-Latfuie' s monograph Brock ^ has given a de- 

 tailed report, to which he has appended a critical examination, 

 through which, however, he comes to quite other conclu- 

 sions than those of the French author. According to him 



* H. von Ihering, he. cit. p. o3. 



t Joyeux-Lati'uie, " Organisation et developpementde I'Oncidie," Thesis 

 in Paris, 1882, pp. l-loSJ, and Arch, de Zool. exper. et gener. x. (1882) 

 pp. 225-383, pis. xiv.-xxii. 



X Loc. cit. p. 148 (372). § Loc. cit. p. 53 (277), pi. xv. fig. 4. 



II Luc. cit. p. 50 (280j. 



*\ J. Brock; in Biol. Centralbl. iii. 12, 1883, pp. 370-374. 



