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Development of the Cephalopods. Though the homologies of the 

 Cephalopoda with the Cephalophorsi, particularly the Pteropods, 

 are quite direct, yet the cuttlefishes differ greatly in their mode of 

 growth, paiticulurly in the einbryological stages. \\ hiie the work 



Sepia, Sepiola, Loligo and Argonauta argo, and they agree so 

 well in their embryology, that the following description answers 

 for all. In the partial segmentation of the yolk, Ussow, as Kolli- 



hirds and the turtle. It begins on one side of the yolk: a pri ni- 

 tive furrow arising, which is intersected at right angles by a second 

 furrow forming four divisions, afterwards eight, until finally a one- 

 layered gerininative disk (blastoderm) is formed on a portion of the 

 surface of the egg, on the second day after development begins. 

 The inner germ-layer then arises, which farther splits into two 

 sub-layers (the outer of which is the dermo-muscular, and the 



In Loligo and Sepiola by the 7th or 8th day the germ becomes 

 organs, the blastoderm covers the entire yolk. The mantle be- 

 On the loth day the gills, funnel, arm- and anal tubercle make 

 their appearance, the germ of the gills arising from the dermo- 



On the lltl/day the rudiments of the auditory organs, the 

 pharynx and salivary glands arise, as well as the anal orifice, and 

 on the succeeding day the auricles of the heart, the pericardium 



lies and veins, with the offshoots of the latter (the so-called 

 kidneys), are developed from the cells of the middle lamella. 



the 13th day the ink-sac develops, and the liver. The intestinal 

 tract originates from the primitive invagination of the outer 

 germ-layer (ectoderm) as in Amphioxus, Ascidia, some Coelen- 



