EARLY ONTOGENETIC PHENOMENA IN MAMMALS. 67 
Teleostean ontogeny are far from being in entire accordance on 
many points. Swaen and Brachet (’99, 04), H. Wilson (’91), 
Sumner (’04), and Boeke (702,07) are among the authors who 
have lately considerably furthered our knowledge of Teleos- 
tean development. The latter author more in particular, 
who adopts my views concerning gastrulation and separates 
that process from what I have proposed to designate as noto- 
genesis, gives certain figures which point in a direction that 
may finally lead to a more close comparison of the processes 
in Amphibia and Mammals on one hand, in ‘l’eleosts on the 
other. I copy a few figures from his latest papers in my 
Figs. 88 and 89 to elucidate how I imagine that it may 
perhaps later be possible to distinguish also in Teleosts a 
protochordal plate (pp) and a protochordal wedge (pw) 
standing in the same relation to each other as in mammals. 
The homologue of the protochordal plate can no doubt be 
detected in a portion of the periblast, to which layer, since 
Boeke’s detailed investigations, participation in the formation 
of embryonic cells can no longer be denied. It is certainly 
striking that this participation is of a nature that would bring 
it in one line with those processes which we have above 
noticed, both in the protochordal plate and in the annular 
zone of entoderm, that is so closely allied with vasifastive 
phenomena. On the other hand the protochordal wedge, as 
a downward proliferation of the ectoderm increasing in length 
by a backward growth of the blastoderm and obtaining after 
some time a new coating of entoderm-cells below it, is quite 
exceptionally evident in Teleosts (Figs. 88, 89). 
The focus of formation of the ventral mesoblast is in 
Teleosts originally far apart from the protochordal wedge, 
but fuses with it when the yolk has been entirely overgrown, 
and when what was at the outset the anterior ring of the 
blastodisc has coalesced from behind with the prostomial 
thickening. This prostomial thickening of Teleosts has since 
Boeke’s researches (’02b) to be looked upon as an entodermal 
(periblastic) proliferation, and is by me homologised with 
that proliferation in the entoderm of mammals which occurs 
