A. E. Verrill — North American Cephalopoda. 



315 



The best and most positive external characters for distingiiishing 

 the sexes, are the hectocotylized condition of the left ventral arm of 

 the male, near the tip (Plate XXIX, fig. 3^ 3^) ; and the presence, in 

 the female, of a horse-shoe shaped sucker, or place for attachment of 

 the spermatophores, on the inner buccal membrane, below the beak 

 (fig. 4, s). These characters, however, are not present in the very 

 young individuals, and in those with the mantle two or three inches 

 long they appear only in a very rudimentary state.* 



The specimen marked An. is from Cape Ann, Mass. (var. borealis); that marked 

 5 E., is var. pallida from Astoria, N. Y. ; the rest are from Vineyard Sound, Mass. 



The adult males have the left ventral arm conspicuously hectocoty- 

 lized (Plate XXIX, figs. 3, 3a) by an alteration and enlargement of 

 the sucker-pedicels and a decrease in the size of the cups of the suckers, 

 some of which usually disappear entirely, especially in the outer row. 

 The modification commences at about the 18th to 20th sucker, by 

 the swelling of the bases of the pedicels ; on siicceeding suckers this 

 rapidly becomes more marked and the swollen bases of the pedicels 

 become more elongated and gradually become compressed trans- 

 versely, while the size of the cups rapidly deci-eases till at about the 

 28tli to 30th they are very minute and rest at the summits of the 

 large, flattened, acute-triangular supports ; from the 30th to 35th the 

 cups usually become mere rudiments or disappear, in large males ; 

 beyond this the cups again grow larg-*r and the pedicels decrease in 

 size, till the small suckers become normal on the tip of the arm. 

 About twenty-five to thirty of the suckers of the outer row are thus 



* Professor Steenstrup formerly advanced the opinion that the males of Octopus and 

 other genera of Cephalopods were provided with the hectocotylized arm from the first, 

 but this we have not found to be the case. The hectocotylized condition of the arm in 

 Loligo is developed in proportion to the development of the internal sexual organs, 

 and is first distinctly noticeable in the larger of the young ones taken in autumn, and 

 in the spring, in the young ones that have survived their first winter. 



Trans. Conn. Acau., Vol. V. 39 February, 1881. 



