in the Cephalopoda. 105 



marked, that along each lateral margin this Hectocotylus bears 

 fine cutaneous papillje in a longitudinal furrow ; these papilla?, 

 which are placed close together, and stand here and there in 

 several close series, gave the fringed margin to the arm in its 

 coiled-up state, and they must also be what were regarded as 

 branchije when the Hectocotylus was considered to be an inde- 

 pendent male organism. In this specimen I was unable to find 

 any trace of a dorsal cavity with an external orifice ; but this 

 would be formed essentially by the covering membrane when 

 the arm was naturally and spontaneously rolled up, — a mode of 

 development which presents no difficulty for the species hitherto 

 obsei'ved, but of which it is difficult to form a clear notion here, 

 on account of the form and position of the enveloping sac. In 

 reference to this it must be mentioned, that the only known 

 Hectocotylus which resembles my fomi in the want of the dorsal 

 cavity and the presence of " brauchise/^ is that found and de- 

 scribed by Kolliker on the female of Tremoctopus violaceus, the 

 development of which, however, is still unknown, as the males 

 of this Cephalopod have not yet been discovered*. 



It seems probable to me, that the vesicular or pyriform, swelled, 

 terminal portion of the Hectocotylus represents the apical plate 

 in Octopus and Eledone, which has already been repeatedly men- 

 tioned, and also that the long filament or " flagellum," which 

 occurs in all Hectocotyli, and originates in all at the same spot, 

 namely where the angle of the fold of skin described in Octopus 

 and Eledone is situated, may be the apex of this angle which has 

 been more developed and elongated (see fig. 4 d) ; only then it 

 cannot be an axial portion. It also appears probable to me, 

 that the muscular membranous border which forms the above- 

 described furrow or semicanal in the hectocotylized arm in Oc- 

 topus and Eledone, which, howevei', is only a peculiar develop- 

 ment of the membrane which runs for a greater or less distance 

 along the arms in all Cephalopoda, may be exactly the same 

 membrane which, in Argonauta and Tremoctopus Carernp, en- 

 velopes the entire Hectocotylus iu its rolled-up state, and which, 

 when the arm is subsequently stripped off, according to the ob- 

 servations of Verany and Vogt, at the same time forms a dorsal 

 cavity at the base of the arm ; whilst, as I'egards its import, 

 this furrow rather corresponds with the internal canal on the 

 dorsal surface of the Hectocotylus, which is destined for the re- 



* Tlie agreement between the Hectocotyli of the two species which have 

 the swimming-membrane between the two uppermost pairs of arms so 

 strongly developed, may serve provisionally as a support for a different 

 distribution of the species under the two generic names Tremoctopus and 

 Philonexis, somewhat as has been attempted by Gray, MoUusca of the 

 British Museum, pp. 24-27. 



