DEVELOPME-NT 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 



Fig. 312. 



Fig. 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; /, the caudal fins; ft, the heart; m, 

 the mantle in which the color- vesicles are already developed and (Kipafile of chang- 

 ing their colors; o, 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.e., 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. 

 116) before the definitive features (Fig. 116) of the cuttle-fish 



