248 
KICHARD ASSHETOX. 
formation of the above-mentioned structures” (‘Quart. Journ. 
Micr. Sci.,’ vol. 31, p. 508). Again : “ This patch of modified 
hypoblast-cells has at the beginning an oval shape, with 
the long axis perpendicular to that of the embryonic shield. 
Part of this patch will develop into the anterior portion of 
the notochord ; for this reason I will call it the protochordal 
plate.” 
How does Hubrecht i-econcile the formation of part of the 
notochord (what I should call the protogenetic portion of the 
notochord) from the gut lining with his theory of the origin 
of the notochord from the supposed fused Actiniau stomodaeum 
according to his present theory? (p. 109). Does Hubrecht 
abandon his earlier conclusions, or does he allow that some of 
the notochord is not formed from the stomod^al protochordal 
wedge ? 
In my humble opinion the Professor was on much sounder 
ground in 1890 than now, althongli, as related elsewhere, I 
cannot follow him in the idea of two gastrulation periods, an 
hypothesis which he has, as we have seen, abandoned since. 
Hut surely the difficulties of coenogenetic and palingenetic 
tissues, of mesoderms of various origin, of notochord of 
epiblastic or hypoblastic origin, are to a large extent 
smoothed away and the problem vastly simplified by an 
appeal to the way the things actually grow in the embryo as 
evidenced by exjierimental observation. 
For we find that there is a part of the organism formed, so 
to speak, on the egg — in situ — roughly radially symme- 
trical, which is what I call the protogenetic ai’ea, and this 
alone represents a gastrula or coelenterate stage. 
To this subsequently is added tissue from a growing point 
(the deuterogenetic area of proliferation), which area itself 
can be called neither epiblast, hypoblast, nor mesoblast; but 
the material produced by active proliferation of this growing 
point becomes epiblast, hypoblast, or inesoblast, according to 
the nature of the layer with which it is in direct con- 
tinuity. 
The protochordal plate and the annular zone inesoblast, 
