NOTES ON AMPHITRETUS. 



95 



there any sign of hectocotylization : the specimen proved to be a female 

 on dissection. 



The suckers number in all 32 — 35 to each arm. For a short stretch 

 —say, of about 14 mm. — at the distal end of arms, they exhibit a 

 tendency to an alternate biserial arrangement. In the remaining, by far 

 the greater portion of the arms, the}' — fourteen or fifteen in number — 

 are arranged in a single row. 



The first sucker, counting from the base of arms, is about 1\ mm. 

 in diameter and is separated from the next following by an interspace 

 of not over 4 mm. In the middle one-third of the arm-length — which 

 space includes about five suckers, say the 7th — 13th — the suckers attain 

 largest size. Here they are set C — 8 mm. apart from one another in a 

 series. 



In the distal one-third of the arm they begin to become gradually 

 smaller and more closely approximated together, until near the arm-tip 

 they are half a millimeter or less in size and are placed in contact with 

 one another. 



Though more or less cylindrical in shape, the suckers are broader 

 at base than at the truncated outer end and usually show a slight 

 constriction near the latter. The height of the largest sucker, leaving 

 the gelatinous envelope totally out of consideration, measures up to 

 4 mm. ; diameter near the base, 3 mm. ; that at the outer end 2-|- mm - 

 The margin is thick and smooth ; the cavity is deep and pore-like. 



Some points of internal organization. 



In order to obtain an insight into the internal structure, incisions 

 and removal of parts have been made, so far of course as could be done 

 without destroying the rare specimen. 



Our attention was first directed to the histological character of the 

 peripheral gelatinous layer. Studying this by means of both sections 

 and teased preparations, we have found, in the first place, the external 

 surface delimited by a fine, wrinkled, structureless membrane, on which 



