CEPHALOPODA OF THE HAWAIIAN ISLANDS. 



283 



into practically a single row on the distal portion of the dorsal arms, contemporaneous with the general 

 atrophy of the arm itself. The suckers of these arms are ultramarginal except as just noted, and the 

 rows very widely spaced; the suckers of the third arms are somewhat intermediate between this con- 

 dition and that which prevails on the ventral pair. 



Male: Body much smaller, perhaps half as large as that of the female, but quite as variable in shape 

 (figure 10 shows the extreme of rotundity V Arms relatively shorter and more delicate than in the 

 female; the four dorsal arms much less highly 

 specialized, their tips normal, and the very 

 delicate webbing not so well developed. Right 

 ventro-lateral arm hectocotylized, the modifica- 

 tion affecting the entire arm, which attains its 

 development in a specialized sac occupying the 

 region which w 7 ould ordinarily be the base of the 

 arm between the base of the funnel and the eye. 

 (Cf. the account given by Steenstrup, 1857, p. 

 103-105.) It is visible through the thin overly- 

 ing integument even in very young specimens 

 as a whitish vermiform body compactly coiled 

 upon itself in such a fashion as to occupy as 

 little space as possible. This arm undergoes a 

 much more rapid growth than the rest of the 

 animal, so that in males measuring about 3 cm. 

 in length (station 4010) the sac is already vigor- 

 ously crowding the eye and funnel and the ani- 

 mal has consequently a somewhat lopsided ap- 

 pearance ; at this stage also the sac has begun to 

 bulge forth by the side of the mouth as a large 

 rounded tumor-like protuberance. In the large 

 mature male from station 40S6, the arm had 

 apparently just broken from its sac, but still re- 

 mained attached by its basal end at the time of 

 capture. At this stage the hectocotylized arm is a 

 highly complex structure as long or longer than 

 the animal itself. It differs very markedly from 

 the hectocotylus of Argonauia and may be 

 briefly described as follows: 



Much flattened; widest about a third of the 

 way above the constricted and bluntly' pointed 

 base. Inner surface bearing about 46 pairs of 

 closely placed suckers ranked in two rather 

 widely interspaced marginal rows; outer surface 

 ornamented with a conspicuous double fringe 

 of long acutely conical papilla;, which extend 

 laterally just above the suckers along the proxi- 

 mal two-thirds of the arm; when the distal 

 third of the arm is reached, the papillae suddenly cease, the outer surface becoming much flattened, 

 naked, and perfectly smooth. Between the rows of papillae the skin is minutely ridged and tuber- 

 cled; near the base an irregular series of small rounded tubercles along the median line gives way 

 on the smooth part to a very fine longitudinal costation ; on either side a flanking series of low rounded 

 transverse ridges persists along the entire papillate portion of the arm. The apparent differentiation 

 of the arm into regions extends even to the suckers, the 27 pairs arming the papillate portion of the arm 

 being very different from the remainder. Here the suckers are crowded, thickened, massive, elevated, 



Fig. 10.— Trcmoctopus violauus, lateral view of adult male, from 

 station 4086. with nearly ripe hectocotylus [225]. X 4. Drawn by 

 R. 1. Hudson. 



