86 Prof. J. Steenstrup on HectocoiyXxx^-formation 



In other species of Loligo both series of acetabula at the apex 

 of the arm are not so uniformly subjected to this metamorphosis, 

 but only one series furnishes the above-mentioned papillae. 

 Amongst the species which I have had the opportunity of 

 examining, this is the case especially in two from the coast of 

 Brazil, namely L. brasiliensis , BI. and L, brevis, Bl., together 

 with a species which agrees well with D'Orbigny's description 

 of his L. gahi, and which is therefore probably derived from 

 the Pacific Ocean. 



Of the last-mentioned species the arm is i-epresented in fig. 3. 

 The left arm is normally constructed as far as the fourteenth 

 acetabulum, after which the peduncles in the outer row of 

 suckers begin to be disproportionately elongated, but still bear 

 small sucking- disks, provided with horny rings, as far as the 

 twenty-second pair, at which the peduncle is quite papilliform, 

 as are all the other peduncles (about twenty-six) which follow 

 it up to the apex; under a strong magnifying power, how- 

 ever, we may still discern a small puncture at the tip of each 

 papilla, — the last indication of the sucking-disk. In the inner 

 row the sucking-disks are continued, witli distinct horny rings, 

 nearly to the apex of the arm (at least they may be traced almost 

 to this with a lens), but they are elevated upon peduncles, 

 which constantly rise higher and higher, so that they completely 

 overtop the piiijillje of the opposite side. It may also be re- 

 marked, that on the inside of each i)apilla a membranous comb 

 or lobe runs down to the median line of the arm, and thence 

 extends in an oblique direction (for it is well known that the 

 suckers arc placed alternately in the two rows) in the form of a 

 similar membranous comb towards the inside of each acetabular 

 peduncle on the opposite side. The development of these mem- 

 branous lobes commences as early as the fourteenth pair*. 



In Loligo brevis, Bl., things are essentially the same; the 

 differences appear to me to be that the sucking- disks which per- 

 sist as far as the apex in the inner series, are not borne upon 

 quite such long peduncles ; that the papillfe, which are very long, 

 especially at their commencement, only make their appearance 

 at the twentieth pair; and that the membranous comb is less 

 developed, although always perceptible. 



Loligo brasiliensis, Bl., of which the Museum possesses two 

 male specimens fioin Rio, has both series of acetabula on the 

 left ventral arm regularly developed as far as the fourteenth pair, 

 and the inner row continues essentially in the same way up to 

 the apex (with thirty-five pairs) ; in the outer series the acetabula 

 diminish rapidly in size, four still exhibiting the sucking-disk 



* From their minuteness, no representation of these membranous lobes 

 could be given. 



