10 Prof. KoLLiKER on the Structure of 



Description of the Hectocotyle q/'Tremoctopus violaceus. 



1. External Form. 



This animal very much resembles the Hectocotyle Octopodis, which Cuvier 

 has described in the ' Annales des Sciences Naturelles' for the year 1829*, the 

 anterior part of the body being long, worm-like, and provided with two rows 

 of suckers on its ventral surface, the posterior short and of an oval shape ; 

 but independently of its being much smaller, it differs also at first sight from 

 H. Octopodis in the back being fringed with a great number of little branchial 

 appendages, and the posterior extremity having a long process. 



The anterior part of the body varies in length from 1^1 f of an inch, is 

 thickest in the middle, and diminishes towards both extremities. Without 

 the branchiae and suckers it would be nearly cylindrical, but in the natural 

 state the cephalic portion is almost quadrangular, while that immediately 

 behind is fiat, and has sharp margins. Its colour is almost entirely pure white ; 

 it exhibits however at the branchiae some azure tints, and here and there some 

 yellowish hues ; there are also some remarkable spots on the back, of which I 

 shall speak presently. The upper surface of this anterior part bears in its 

 cephalic portion the branchial appendages and the spots just mentioned ; the 

 upper surface of the posterior portion, on the contrary, is perfectly smooth ; 

 the spots are arranged in two slightly-irregular rows between the branchiae 

 along the middle of the back ; they are circular, about -aV^ of a line in 

 diameter, of a brown or violet colour, and about 50 in number. The branchial 

 appendages are placed on a low, mantle-like margin, which takes its origin 

 from the side of the animal between the suckers and the coloured spots ; the 

 appendages have a conical form, are 1 line long and ^th of a line broad : 

 during life those next to the middle of the back stand vertically erect, the 

 others successively assume a more inclined direction, and the outermost lie 

 nearly transversely. The appendages are disposed in irregular longitudinal 

 lines ; their number is considerable, amounting to about 250 on each side. 



The ventral surface of the anterior part is quite smooth in the middle, and 

 slightly convex from side to side ; on each of its margins are situated 40 or 4 1 



* Ire S6rie, t. xviii. p. 147. 



