348 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [138] 



The ratio of the diameter of the largest tentacular suckers to the 

 mantle-length varies, in the male, from 1:50 to 1:90, averaging about 

 1:65; iu the female it varies from 1:30 to 1:54, averaging about 1:45. 



The proportion of the length of the dorsal arms to the mantle-length, 

 in the male, averages about 1:3.50; in the female about 1:2.75. 



The pen of the female is relatively broader and shorter than that of 

 the male (see Table A). 



The best and most positive external characters for distinguishing the 

 sexes are the heetocotylized condition of the left ventral arm of the 

 male, near the tip (Plate XXVI, figs. 3, 3 a), and the presence, in the 

 female, of a horseshoe-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 indi- 

 viduals, 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 $ E is var. pallida, 

 from Astoria, N. V. ; the rest are from Vineyard Sound, Mass. 



The adult males have the left ventral arm conspicuously heetocoty- 

 lized (Plate XXYI, figs. 3, 3 a) 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 succeeding suckers this rapidly 

 becomes more marked, and the swollen bases of the pedicels become 

 more elongated and gradually become compressed transversely, while 

 the size of the cups rapidly decreases till at about the 28th 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 larger and the pedicels decrease in size, till the small' suckers 

 become normal on the tip of the arm. About twenty-five to thirty of 



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

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

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

 Lol'ujo 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. 



