516 H. p. KJERSCHOW AGERSBORG 



(2) The Dorsal Tentacles or'Ehinophores'. 



On the outside of the veil, in M. leonina, is a pair of 

 tentacles, supposed to be equal to the posterior pair in, e.g., 

 Aeolidia Cuvier (1798). According to the original descrip- 

 tion of the genus Melibe by Rang (1829) the tentacles are ' au 

 nombre de deux, situes a la base du voile, tres allonges, coniques, 

 termines par une petite capsule, de laquelle sort un organe 

 conique et retractile ' ; Gould (1852), in his description of 

 Chioraera leonina (s. Melibe leonina), points out: 

 ' . . . tentaculae cephalicae foliatae, retractiles ; ' and Pease 

 (1860) for M. pilosa says: 'Tentacles on the posterior 

 portion of the veil rather remote, small, ovate, closely and 

 transversely lamellated and retractile into long trumpet- 

 shaped sheaths, which are furnished with laciniated appendages.' 

 Again, Tapparone-Canefri (1876) for Jacunia (s. Melibe) 

 papillosa de Filippi, states: ' Tentacula (Rhynophoria) 

 laminata, tenuia, apice obtusiuscula, retractilia, e vagina 

 caliciformi angusta vix proeminentia.' Cooper (1863) and 

 Fewkes (1889) are content with the description of Gould ; 

 neither of them mentions tentacles. Alder and Hancock 

 (1864) refer to these organs as dorsal tentacles. The largest 

 part of the tentacles in Melibe is the tentacular stalks ; they 

 are wedge-shaped bodies (PI. 27, figs. 3, 8) somewhat rounded 

 at their base. The wedge is like a broad axe, the edge of which 

 is a little curved. They are arranged at right angles to each 

 other, and this angle would intersect posterior to their base 

 in the mid-dorsal line of the hood. Along the edge of the curved 

 wedges are slits, in one of which, on the inner part of the curve, 

 i.e. not on the apical part of the tentacle — except when it 

 is expanded — is a small organ (PL 27, fig. 8, Rh), the real 

 tentacle, that may be retracted below the surface of the 

 wedge-shaped tentacular stalks (vide Agersborg, 1923, figs. 4, 

 5, pa). Gould, in describing these, says : ' On the top of the 

 head are two foliate expansions destitute of venations, which 

 answer to the true tentacles ; on their anterior edge is an opaque 

 whitish papilla, presenting something of a spiral or lamellar 



