DEVELOPMENT OF EMBEYO. 



603 



(1610.) Although we mean to defer any minute account of the de- 

 velopment of the embryo in ovo until an examination of the eggs of ovi- 

 parous Vertebrata shall afford more ample materials for elucidating this 

 important subject, it will be as well in this place briefly to notice the 

 condition of the young Cephalopods previous to their escape from the 



Fig. 301. 



Fig. 302. 



A male Tremoctopus, seen from 

 the ventral aspect. The visceral sac 

 has been laid open and the left 

 half of the mantle turned aside, to 

 show the branchia and the opening 

 of the generative apparatus during 

 the expulsion of the spermatophore. 

 a, sacculus containing the Hectoco- 

 tylus ; b, branchia of the left side, 

 with its branchial heart, c; d, the 

 " bottle," from which the spermato- 

 phore (e) is in progress of expul- 

 sion; //, the mantle. 



Tremoctopus carina (male), 

 showing the Hectocotylus (a) 

 in its ordinary position. 



egg, wherein the first part of their growth is accomplished. Before 

 the egg is hatched, the foetal Cuttle-fish already presents all the organs 

 essential to its support and preservation : the tentacula upon the head, 

 the eyes, the respiratory apparatus, and even the ink-bag, which in the 

 earlier stages of growth were quite undistinguishable in the germ of 

 the future being (fig. 303, 1), slowly make their appearance ; so that be- 

 fore birth the little creature presents most of the peculiarities which 

 characterize the species to which it belongs. But the most prominent 

 feature that strikes the attention of the physiologist is the remarkable 

 position of the duct communicating between the yelk of the egg (the 

 great reservoir of nourishment provided by nature for the support of the 

 foetus whilst retained in the egg) and the alimentary canal of the as yet 



