418 A. A. W. HUBRECHT. 
it becomes evident that the Craniota have not sprung from 
this acraniate animal; that the relation between the anterior 
extremity of the notochord and the brain must have been 
different in the real ancestral Vertebrates; that eyes and 
static organs (otoliths) cannot have been absent in those 
ancestors as they are in Amphioxus—in short, that Dohrn was 
quite right when he proclaimed Amphioxus to be a distantly 
related, partly degenerated, relict, which could not furnish 
us with important conclusions concerning the phylogeny of 
Vertebrates. 
We find in Amphioxus when we try to compare it with the 
higher Vertebrates the same difficulties which we encounter 
when comparing the Cyclostomes with the other fishes or the 
Ornithodelphia with the higher mammals. All three are 
representatives of old and early stems that have branched off 
sideways at a very early stage, and that thus represent 
lateral lines of development. They have no considerable 
significance for comparative phylogeny, and may on no account 
be looked upon as transitional forms that occupy a place on 
the line of descent between the Ccelenterates and the Primates. 
Once we have fixed upon this position for Amphioxus in 
the system, there will be no difficulty in looking upon the sub- 
divisions Acrania and Craniota as being equivalent to a 
new subdivision, Invaginata and Delaminata. The pro- 
cess of invagination, which is noticed in so many Vertebrates as 
accompanying the origin of the notochord and the somites, will 
not, then, any longer be indicated by the name gastrulation. 
Together with this the significance of the primitive streak 
as coalesced lips of the blastopore will have to be abandoned; 
the streak and the groove represent the oral slit of the 
Actinia with its dependent stomodzum, which, when com- 
pressed into the notochord, would thus be homologous to that 
organ in Vertebrates. 
I feel very hopeful that on this basis a mutual under- 
standing will soon be arrived at, by which many embryo- 
logical results which up to now seem hopelessly confused 
will fall into line. 
