DEVELOPMENT OF CUTTLE-FISHES. 



279 



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 



PIG. 217. 



PIG. 218. 



Fig. 217. Embryo of Loligo Pealii. a, a", a'", a"", the right arms belonging to 

 four pairs ; c, the side of the head ; , the eye ; /, the caudal fins ; h, the heart ; m, 



218 the same. Both after Verrill. 



large yolk sac, as in Figs. 217, 218. Finally the young cut- 

 tle-fish hatches in the form indicated by Fig. 219, 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 segment- 

 ation of the yolk, assumed a trochosphere condition (Fig. 220) 

 before the definitive features (Fig. 221) of the cuttle-fish 



