242 
EICHAED ASSHETON. 
Sci./ vol. 49, in which he says that I quite misunderstood 
his German version, in so far as I believed him to “hold the 
vertebrate mouth to be in any way derived from the stomo- 
daeum of an Actinia-like animal.” I am sorry I made the 
mistake, which I made at least by implication, confounding 
in my mind Hubrecht’s with Sedgwick^s very similar theory, 
published in 1884, to which, by the w^ay, Hubrecht made no 
reference when he put his forward in 1902. 
The accompanying text-fig. 2 shows clearly enough what is 
the difference between Hubrecht’s conception and mine, and 
why I prefer protogenesis and deuterogenesis to kephalo- 
genesis and notogenesis. 
The aboral surface of the coelenterate, according to 
Hubrecht, becomes the ventral surface of a vertebrate ; 
according to my interpretation the aboral surface becomes 
the anterior. According to Hubrecht the oral surface of the 
coelenterate becomes the dorsal surface of the vertebrate ; 
according to me the oral surface of the coelenterate is the 
posterior surface of the vertebrate, and so on, as shown in 
the figure. 
I claim that my interpretation is founded upon actual 
experiment on the living embryo, which can be tested by 
an}'one. 
Where can Hubrecht find experimental evidence in support 
of the elongation of an actinian or other mouth in, for instance^ 
the frog, with concrescence or coalescence of its walls ? Or 
how can a theory of concrescence be reconciled with experi- 
ments such as those of Kopsch on the trout? 
I claim that the experiments which I described in my 
paper of 1905 prove that in the frog at any rate the embryo 
does grow in the way illustrated by my figures, and that this 
is absolutely opposed to tlie method of growth required by 
Hubrecht’s theory. 
Again, with reference to notogenesis, Hubrecht seems 
to have no very clear conception as to tlie extent of its 
influence. In his paper on Gastrulation ” (’06), he defines 
kephalogenesis and notogenesis thus : “ The distinction 
