Text-fig. 2. 
a. 
CL 
CL. 
Diagium to show the difference in the conception of kephalo- 
genesis and notogenesis on the one hand and protogenesis and 
denterogenesis on the other. The middle figure, (3, represents 
the gastraea or early coelenterate stage, with blastopore on the 
lower surface. The upper figiu’e, a, represents the vertebrate 
according to Hubi-echt, derived by elongation of the gastrula 
in the direction v d, producing an elongated actinian stomo- 
damm, followed by concrescence of the walls of the stomodseuni 
to foiTu the notochord. The lower figure, y, represents the 
vertebrate according to the author's conception by elongation 
of the gastrula in the direction a p by activity of cells forming 
the blastopore lip. Subsequently, the activity of the ventral 
part dies out, and the more dorsal paid continues active and 
fonns the tail. 
