DEVELOPMENT OF CUTTLE-FISHES. 259 
and a day later the rudiments of the ears, of the pharynx 
and salivary glands ; while a day or two after, the ventri- 
cle, auricles, the kidneys, the ink-sac, and liver develop. 
Contrary to the usual rule the ganglia arise from the middle 
instead of the outer germ-layer. After this the germ grad- 
ually develops until it rises above the surface of the egg, 
and soon the yolk is partly absorbed and is contained in a 
Fie. 212, Fie. 213, 
Fig. 212.—Embryo of Loligo Pealii. a, a’,a’’, a’’’’, the right arms belonging to 
four pairs; c, the side of the head; e, the eye; jf, the caudal fins; h, the heart; m, 
the mantle in which the color-vesicles are already developed and capable of chang- 
ing their colors; 0, the internal cavity of the ears; s, siphon.—After Verrill. 
Fig. 213.—The same as Fig. 212, but more advanced. The lettering in Figs. 212 
and 213 the same.—Both after Verrill. 
. large yoke sac, as in Figs, 212, 213. Finally the young cut- 
tle-fish hatches in the form indicated by Fig. 214, and then 
swims free upon the surface of the sea. 
The development of Cephalopods in general is, then, di- 
rect, i.¢., there is no metamorphosis, the phases of meta- 
morphosis seen in most other mollusks not appearing; but 
in an unknown species of cuttle-fish whose eggs were found 
floating on the Atlantic, the germ, after the partial segmen- 
tation of the yoke, assumed a free-swimming condition (Fig. 
115) before the definitive features (Fig. 116) of the cuttle-fish 
