150 
RICHARD ASSIIETON. 
Amniota), then that blastopore may close by concrescence, 
bnt the two processes are entirely different phenomena. 
I have myself tried for years to emphasise this difference 
(’9d, ’96, ’08, ’09), and the difference is recognised by many 
embryologists such ns Hertwig, Hubrecht, Keibel, MacBride, 
although they do not use the terms which I humbly protest 
do most correctly express the essence of the process, namely 
protogenesis and deuterogenesis. The phenomenon of gas- 
trulation or the formation of the primitive gut-cavity or 
archenteron, whether with or without a blastopore, is proto- 
genetic, and represents a more ancient phase of evolution. 
'J’he subsequent phenomenon of deuterogenesis is growth in 
length and is post-gastrula, and in those animals which have 
a blastopore formed in connection with the first appearance 
of gut-cavity it involves all the changes by which the blasto- 
pore becomes wholly or partially closed, whether by coales- 
cence, convergence, or concrescence, partial or total. It 
represents a stage in evolution subsequent to that represented 
by the gastrula stage. 
If there is any concrescence it is concerned with deutero- 
genesis in the vertebrates and not with gastnilation ; but it 
is extremely doubtful, in spite of Patterson’s work, whether 
there is any such thing as concrescence in the sense which 
can be interpreted as meaning that the embryo of the 
vertebrate is formed by the fusion of the lips of an elongated 
blastopore. 
Patterson adheres with patriotic tenacity to the view so 
commonly held by Americans as to the formation of the 
vertebrate embryo by concrescence. He writes thus on p. 
103 : " In other word.s, in the teleost the entire margin of 
the blastoderm separates from the periblast, and this entire 
margin (g’erm-i-ing) concresces to form the embryo.” He was 
presumably unaware of Kopsch’s woi k on the eggs of Salmo, 
1905, or he could not possibly have written so dogmatically. 
Kopsch’s expeiuments prove as conclusively (so it seems to 
me) as anything can be proved that in the trout the main 
dorsal axis of the embryo is not formed by concrescence. 
