116 
3 
trulation which, accordingly, in Vertebrates is always 
performed by delamination (HUBRECHT, 1902, p. 71), though 
of course an exception must be made for Armphioxus. 
This, truly, might appear a serious obstacle but it can easily 
be overcome by no longer recognizing “the holy Amphioxus” 
(ibid. p. 68) as the most primitive Chordate. 
Thus HUBRECHT (1905), in agreement with ASSHETON and 
going still one step further than BRACHET, now adheres 
to the view: “Sobald der sogenannte Blastoporus auftritt, 
der “als Rusconischer After eine Strecke weit um die 
Eioberfläche wandert, um schliesslich vielfach in den 
definitiven Anus verwandelt zu werden, haben wir es nicht 
mehr mit dem Gastrulationsprozess, sondern mit jenem der 
Bildung des metameren, bilateral-symmetrischen Rückens 
und der Chorda zu tun”. This process in termed “notogenesis” 
by HUBRECHT. 
Let us now first have a look at the process which in my 
opinion is the gastrulation of Vertebrates but which according 
to the above cited authors either indicates the end or comes 
only after the gastrulation and which is interpreted in entirely 
different ways, At the surface of the egg this stage IS 
characterized by the formation and the contraction of the 
blastopore border. Though, as we shall see, hardly two authors 
agree in regard to the place where this border, e.g. in the 
Amphibian egg, first appears and how exactly it moves over 
the surface of the egg, there is now a fairly general agreement 
that the closure is performed in a rostro-caudad eccentric way 
and that the dorsal lip which is also the first to appear, In 
the shape of a crescent, moves much faster than the ventral 
lip which remains almost stationary. In Invertebrates 
RHUMBLER (1902) reached the conclusion that the entoderm 
cells particularly play an active rôle at the gastrulation 
process and in Vertebrates we get the same impression. 
Their tendency to sink into the interior of the egg IS 
already evident in the blastula-stage, as is the case In 
Invertebrates where often the entoderm cells elongate con- 
siderably before invagination begins. It is also this phe- 
nomenon which has led BRACHET to his conception of à 
“clivage gastruléen.” Proliferating and growing inwards 
under the border of the blastopore the entoderm-celis then 
form the archenteron, and since this process also goes on 
more actively under the dorsal than under the ventral lip, 
the part of the archenteron formed here is much more 
