CEPHALOPODA. 65 



dom have fins. They are the most eccentric or " aberrant" mollusks, supe- 

 rior in organization to all the rest, but manifesting some remarkable and 

 unexpected analogies with the lowest classes of animals. 



The males of some species of octopus and eledone, are similar to the fe- 

 males, but are comparatively scarce. Only the females of many others are 

 known, and every specimen of the argonaut hitherto examined (amounting to 

 many hundreds), has been of that sex. Dr. Albert Kolliker has suggested 

 that the real males of the argonaut, and also of octojms granidatus and 

 tremoctopus violaceus are the hectocotyles, previously mistaken for parasitic 

 worms. 



The hectocoiyJe of octopus granulatus was described by Cuvier,* who ob- 

 tained several specimens from octopods captm-ed in the Mediterranean. It is 

 five inches in length, and resembles a detached arm of the octopus, its under 

 surface being bordered with 40 or 50 pairs of alternate suckers. 



The liectocotijle of tremoctopus was discovered by Dr. Kolliker, at Messina, 

 in 1842, adhering to the interior of the gill-chamber and funnel of the 

 poulpe ; it is represented in PI. I., fig. 3. The body is worm-like, with two 

 rows of suckers on the ventral surface, and an oval appendage at the posterior 

 end. The anterior part of tlie back is fringed with a double series of bran- 

 chial filaments (250 on each side). Between the branchiae are two rows of 

 brown or violet spots, like the pigment cells of the tremoctopus. The suckers 

 (40 on each side) closely resemble those of the tremoctopus, in miniature. 

 Between the suckers are four or five series of pores, the openings of minute 

 canals, passing into the abdominal cavity. The mouth is at the anterior 

 extremity, and is minute and simple ; the alimentary canal runs straight 

 through the body, nearly filling it. The heart is in the middle of the back, 

 between the branchiee ; it consists of an auricle and a ventricle, and gives 

 origin to two large vessels. There is also an artery and vein on each side, 

 giving branches to the branchial filaments. A nerve extends along the in- 

 testine, and one ganglion has been observed. The oval sac incloses a small 

 but very long convoluted tube, ending in a muscular vas deferens ; it contains 

 iannmeviihle speriiiatozoa. 



The hectocoiyle of the argonaut was discovered by Chiaje, who considered 

 it a parasitic worm, and described it under the name of trichocephahis aceta- 

 hularis ; it was again described by Costa,\ w'ho regarded it as " a spermato- 

 phore of singular shape ;" and lastly by Dr. KoUiker.:|: 



It is similar in form to the others, but is only seven lines in length, and 

 has a filiform appendage in fi'ont, six lines long. It has tv^o rows of alternate 



• An. Sc. Nat. I Series, t. 18. p. 147. 1829. 

 t An. Sc. Nat. 2 Series, 7. p. 173. 



X Lin. Trans. Vol. 20, pt. 1, p. 9; and in his own zootomical berichte, where it is 

 figured. 



