CEPHALOPODA. 161 
anterior ends are continuous and attached; the posterior ends 
are at first free, but eventually uniting they form the funnel 
ps. ‘The rudimentary gills b appear between the epipodiwm 
and mantle. The alimentary canal is at first straight; (the 
mouth being at a, the vent at b, in Fig. 35 A). The embryo 
now grows faster in a vertical than in a longitudinal direction, 
so that it takes on the cephalopodic 
form. The intestine, as a consequence, 
becomes bent upon itself; and the and 
terior pair of arms grow over in front 
of the head, and unite, so as eventually 
to throw the mouth nearly into the 
centre of the arms.” (Huxley.) At a 
later period of development (Fig. 35, D), 
the respiratory movements are per- 
formed by the alternate dilatation and 
contraction of the mantle; and the ink- 
bag is conspicuous by the colour of its 
contents. At the period of exclusion 
from the nidimental capsule, fine layers 
of the shell of the young cuttle-fish 
haye been formed; but except the 
nucleus, which is calcified, they are Fig.36. Argonaut, embryo 
horny and transparent. The lateral aes 
fins are broader than in the mature animal. The embryo of 
the Argonaut, as described by Kolliker, has simple conical 
arms (1—4, Fig. 36); and indications of the funnel appear as 
a ridge, p, on each side of the body; v is the yolk sac; o the 
position of the future mouth; e the eye; b the gill; and m the 
mantle. 
Famity I.—ARGONAUTIDA. 
Dorsal arms (of the female) webbed at the extremity, secreting 
asymmetrical inyoluted shell. Third left arm in male hecto- 
cotylised ; deciduous, colourless, developed in a sac. Female 
polyandrous. Mantle supported in front by a single ridge on 
the funnel. 
Genus ARGonAUTA, Lin. Argonaut, or paper sailor. 
Etymology, argonautai, sailors of the ship Argo. 
Synonyms, ocythoé (Rafinesque). Nautilus (Aristotle and 
Pliny), 
