412 A. A. W. HUBRECHT. 
augurated (comparable to the origin of the metamerical worm 
out of the trochophora larva) by which the notochord and 
the somites, 1. e. the bilaterally symmetrical metameric animal 
are called into existence. 
And so this latter process must necessarily correspond—if 
we go back into phylogeny only far enough—to the transition 
of the gastrula larva into the longitudinally stretched Actinia- 
hike animal. We have already demonstrated above that it is 
irrational to continue to use the term “ gastrulation” for this 
phase of development. The cclomic diverticula of the 
Actinia that are yet in continuity with the intestine are the 
predecessors of the somites, the nerve-ring on the oral disk 
that of the medulla, the stomodzum stands for the notochord 
and the oval slit of the Actinia (no primitive mouth or blasto- 
pore!) is reflected in the primitive groove which is in so natural 
a continuity with the notochord. 
In a former publication! I have distinguished simultaneously 
with Keibel,? but independently of him, two phases in the 
gastrulation process, of which the second was erroneously 
termed ‘the palingenetic phase of gastrulation.” Itis identical 
with the second process above described, which has only 
certain superficial analogies with gastrulation by invagination, 
and which, nevertheless, is bound up quite as closely to the 
real gastrulation as is the growth of the elongated Actinia 
to that of the gastrula-larva. 
The primitive mouth of the Actinia-gastrula is gradually 
elongated into the mouth-sht of the Actinia, which in its turn 
leads into the stomodeum. The blastoporus of the Erinaceus- 
gastrula, which very soon closes up again, lengthens out 
posteriorly in the primitive groove, the floor of which—the 
primitive streak—produces the material for the notochord. 
There is, then, during ontogeny an unbroken continuity 
between the blastopore of the Actinian and its oral slit, 
1 «Anat. Anzeiger,’ iii, 1888, p. 911; ‘ Quart. Journ. of Micr. Science,’ vol. 
xxxi, 1890, p. 552. 
2 « Zur Entwickelungsgeschichte der Chorda, etc.,” ‘Archiv f. Anat. u. 
Physiol., Anat. Abth.,’ 1889, p. 376. 
