THE CUTTLE-FISH. 
117 
arms round the head. These forms are the argonaut and the 
nautilus and ammonites. 
The argonaut, sometimes called the paper-sailor, is best 
known by its beautifully delicate and translucent shell (PI. XLI. 
fig. 3), which, unlike the cuttle bone, has no organic connection 
with the body of the animal possessing it. 
The creature has eight arms, but two of these are enormously 
expanded towards their ends ; and the popular belief was that the 
argonaut sat in its shell with these expanded arms raised to act as 
sails, while with the others it propelled its boat by rowing. Its 
mode of locomotion, however, is really by the ejection of water 
from the funnel, and these expanded arms serve the singular office 
of secreting the shell over which they are externally applied 
(PI. XLI. fig. 3). Hence this shell is termed a pedal shell,” 
from its mode of formation, while the sepiostaire of. the cuttle- 
fish is called a pallial shell,” because it is formed in the sub- 
stance of the mantle. 
The argonaut presents another very singular peculiarity. 
For a long time — indeed, until the last few years — none but 
females were found ; but Cuvier discovered in the pallial 
chamber of one of these an elongated organised body covered 
with suckers, and containing a hollow chamber. The great 
naturalist placed it amongst the parasitic worms, and named it 
Hectocotylus. Subsequently Hr. Kolliker noticed the presence 
of chromatophores, and also of a multitude of spermatozoa in 
the hollow chamber ; and he concluded that the organism was 
a male argonaut, which thus would be an animal quite dissimilar 
in form to the female, and rudimentary in size as compared to 
her. Such sexual discrepancy, however, is well known to exist 
in many of the lower animals ; so that the idea, though start- 
ling, was by no means incredible. 
Since Kolliker’s observations, however, the true male (fig. 4) 
has been found by Henry Miller andVerany of Grenoa, and it turns 
out to be an animal like the female, except that it is consider- 
ably smaller, and has no shell and no expanded arms. What, 
then, is the Hectocotylus of Cuvier ? Why, it turns out to be 
nothing less than one of the tentacles of the male (fig. 4 A), 
who, in paying his addresses, not only offers his hand, or rather 
arm, but actually leaves it behind him in the pallial chamber 
of the female ! 
This peculiar action is not known to occur in any other 
cephalopod ; nevertheless, all of them are sexually distinguished 
by some modification of one of the arms, as has been already 
noticed with regard to our type. 
The nautilus (fig. 6) is an animal more different from the 
cuttle-fish than is the argonaut, though still belonging to the same 
class. It is found in the Chinese Sea and Indian Ocean, but is 
