5'22 H. p. KJERSCHOW AGERSBORG 



Hancock and Embleton (184iS: 108), who wrote : ' The func- 

 tion of respiration we believe to be performed by the whole 

 surface of the skin, including the papillae, the skin of the 

 back and of the sides between the papillae, and the entire 

 surface of the latter organs. . . .' It may, therefore, be quite 

 incorrect to designate these 'branchial lobes' cerata; 

 moreover, this term stands nearer ctenidium or true gill in 

 meaning, and on that account, and for the reason stated by 

 Bergh, and the facts recorded by Hancock and Embleton, 

 papillae may be the most appropriate term. The T e t h y m e - 

 libidae being cladohepatic nudibranchs, of course, come 

 under this terminology. Bergh also uses the term papillae 

 for the Tethymelibidae, and is the most consistent 

 writer in this as well as in other respects relative to the 

 nomenclature he employs. 



Melibe leonina has six pairs of papillae, alternating in 

 position (PL 27, figs. 1, 8). They appear smooth to the naked 

 eye, but fundamentally they are tufted or fimbriated as 

 in M. fimbriata Alder and Hancock, M. bucephala 

 Bergh, and Tethys leporina Linnaeus, although in 

 M. leonina (Gould) the fimbriated condition of the papillae 

 is hardly distinguishal)le. The first pair is located dorsad and 

 a little posterior to the genital pores, and approximately in line 

 with the hepatic junction to the stomach. The arrangement, the 

 size, shape, and structure of the papillae may be seen in PI. 27, 

 figs. 1, 8, and PI. 80, figs. 18-25 respectively. Microscopically, 

 the papillae show two principal morphological constituents, 

 viz. (1) terminating branches of the liver (the brownish vascular 

 ramifications of (lould), and (2) smooth muscle-fibres ; but 

 also vascular spaces (PI. 80, fig. 25, Osp), odoriferous glands 

 {Og), and a tubercular surface (Thr). But the papillae are, 

 however, subject to variation in their structure, depending 

 on the age and the position of the papilla. The two anterior 

 pairs (PI. 80, figs. IS -21) are far more profusely supplied with 

 hepatic diverticula and muscle-fibres than are the remaining 

 pairs (PI. 80, figs. 22-4). The last pair does not seem to have 

 any appreciable amount of muscle-fibres or liver-branches. 



