BOOK ELEVENTH. 
CHEPHALOPODA. 
CLASSIFICATION, 
§ 230. 
Tue CxpHatoropa present, in their organization both internal and 
external, so many peculiarities which distinguish them from all the other 
Mollusea, that it is necessary to consider them in a class by themselves, 
although their genera are not numerous. 
It is, moreover, necessary to state why we here regard the different forms 
of Hectocotylus which hitherto have been considered as parasites of these ani- 
mals,.as the males of certain Octopoda. The researches of Kolliker have 
led us to make this change. This naturalist founds his opinion upon the 
following convincing reasons:® The specimens of Hectocotylus have bran- 
chiae, and a heart with arteries and veins, and they cannot, therefore, be 
regarded as Helminthes. On the other hand, they have, in common with the 
Cephalopoda, the contractile chromatophoric cells of the skin, and the same 
kind of spermatic particles and suckers; and the muscular substance of 
their body is arranged exactly like that of the arms of the Cephalopoda. 
All of them are males, and the Cephalopoda, with which they are connected, 
are all females; finally, the embryos found in the eggs of certain Octopoda 
exactly resemble them. Whoever has had the opportunity of examining the 
species yet known, viz: Hectocotylus argonautae, octopodis, and tremoctopo- 
1 At present there are known two or three species XVIII. 1829, p. 147, Pl. XI. A. fig. 1 5, or Fro- 
of these singular beings resembling the torn-off 
arms of the Octopoda, and which live in the cavity 
of the mantle of certain Octopoda, attached by 
the means of suckers, Hectocotylus argonautae 
was first described quite imperfectly by Delle Chi- 
‘aje (Memor. &c. II. p. 225, Tav. XVI. fig. 1, 2, 
and Isis, 1832, Taf. X. fig. 12, a. b.) under 
the name of Trichocephalus acetabularis. An- 
other description by Costa (Ann. de Sc. Nat. 
XVI. 1841, p. 184, Pl. XIII. fig. 2, a.-c.) has not 
added much to our knowledge of the real nature of 
this animal. Another species, Hectocotylus octo- 
podis, established by Cuvier (Ann. d. Sc. Nat. 
riep’s Not. XXVIL. 1830, p. 6, fig. 16-19, ur Isis, 
1832, p. 559, Taf. IX. fig. 1-5) should be found in 
the cavity of the mantle of Octopus sranulatus 
(Lamarck). It is probably identical with Octopus 
tuberculatus of Delle Chiaje (Octopus Verany, 
Wagner), which lives in the Mediterranean Sea, 
and perhaps, also, with T'remoctopus violaceus. 
If this last is not so, there is then a third species 
of Hectocotylus, viz: the male of Tremoctopus 
violaceus, 
2See Kélliker, On the Hectocotylus of Tre- 
moctopus violaceus, and Argonauta argo, in 
the Ann. of Nat. Hist. XVI. 1846, p. 414. 
