102 Prof. J. Steenstrup on Htciocoiyhx^-formation 



the opposite one has 93, so that the deficiency is about one- 

 third. A strong cutaneous border commences in the middle of 

 the margin of the membrane stretched between the third and 

 fourth arms, and thence runs along the arm to its apex, where 

 there is a pecuharly developed terminal portion, destitute of 

 suckers, which evidently represents the spoon-shaped plate of 

 the Octopods, but which is furnished with several elevated lon- 

 gitudinal folds. The individual figured also deserves notice, 

 because the seven other arras are not provided with acetabula at 

 the extremities, but with two rows of cutaneous laminae, a pecu- 

 liarity which I do not find described in any Eledone^ and which 

 therefore made me doubt for some time whether I had not a 

 new and undescribed species before me. As, however, two male 

 specimens* afterwards examined, of which one at all events was 

 from the Mediterranean, were also destitute of acetabula at the 

 apex of the arms, and bore similar laminae in their place, whilst 

 I could not find the least trace of anything of the kind in nu- 

 merous females of Eledone from the Mediterranean, I assume 

 that this peculiar development of the extremities of the arms 

 only occurs in the males, so that it is a sexual character (see 

 %. 5"). 



In this opinion I am the more strengthened as I find exactly 

 corresponding cutaneous formations at the extreme ends of the 

 arms in a large male Eledone from Bergen, which is certainly 

 E. cin^osa, Lamk., whilst several females, partly from the same 

 locality, and partly from other places on the Norwegian coast 

 and from Faero, exhibit no trace of it. Nevertheless, in the last- 

 mentioned species these cutaneous lobes differ from those occur- 

 ring in E. moschata, in being less foliaceous or plate-like, but 

 more elongated and thin, almost like cirri or filaments. Fig. 6 

 represents a small portion of them from one of the arms, but 

 certainly from a specimen which was in a rather flabby state. 



In opposition to the great uncertainty which prevails in this 

 genus in the recognition of the species in consequence of the 

 want of definite external characters f, these observations upon 

 the different development of the apices of the arms in the two 

 sexes and in different species, may conduct us to the right way, 

 when they are extended to all described species. 



* In these individuals the third right arm had respectively 62 and 65 

 developed acetabula. 



t A want which is so great, that the species which have been regarded 

 as far removed from each other, are essentially distinguished, in that some 

 have a cirrus over the eye, the others not (although this cirrus appears 

 always to be more or less distinctly present), whilst the more nearly related 

 species are not to be distinguished even from spirit specimens. See Verany, 

 Mollusques Mediterraneens, p. 15 : "car, je I'ai deja dit, a{)res la mort les 

 deux especes sont, si je peux m'exprimer ainsi, inde'chifFrablcs." 



