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remark, this line continues to the fore-end of the cerebral-plate, the 
animal pole, where the blastopore has never been. For concrescence 
at the hind border of the blastopore still less evidence can be 
adduced. The groove between the slit-like blastopore and the anal 
pit does not become gradually longer, as might be expected in this 
case, the anal pit removing from the ventral border of the blastopore, 
but on the contrary it only gradually becomes more distinct and at 
the same time shorter, the blastopore approaching the anal pit. 
Evidently it is not to be considered as a concrescence-seam, perhaps 
it may be compared to the groove joining the two impressions made 
by two fingers pressed near one another into a soft cushion. 
Concerning the relation between blastopore and anus in vertebrates 
three suppositions may be made: 
1. there is a primary relation 
2. there is no relation 
3. there is a secondary relation. 
The first supposition mentioned above is now the most widely 
accepted, even where in Anurans 2. seems to prevail yet it is 
assumed that this is to be traced back to 1. since what is found 
in Urodelans must be valid for Anurans. Thus Mavrer (1906) in 
Hertwie’s Handbuch tries to trace back all the results for chordates 
to 1, though the evidence adduced is not always equally convincing. 
Already in Amphioxus no relation between the anus and the blasto- 
pore has as yet been discovered. 
The possibility of 1. is in no way excluded by my theory, which 
derives chordates in opposition to GROBBEN from Protostomia, as long 
as the possibility of a relation between the anus and the blastopore 
in the latter group exists, as might be expected from SEDGWICK’s 
well-known theory (1884), which derives the mouth and the anus of 
Bilateria from the anterior and the posterior extremity of a slit-like 
actinian mouth of which the borders coalesce in the middle. The 
concrescence-seam joining mouth and anus, which according to this 
theory should run over the ventral side of annelids, ought to be 
able to be traced in vertebrates too then in the groove between 
anus and blastopore, that is in the so-called ““Afterrinne”, the “pri- 
mitive streak” of Ropinson and AssHEToN (see above) — not in the 
hypothetical concrescence-raphe in front of the blastopore, the ‘‘pri- 
mitive streak” of the theory of concrescence, as LAMEERE (1891) and 
HuBreenrt (1905) assume in their application of Sepewick’s theory 
on Vertebrates. Thus the presence of a primary relation between 
the anus and the blastopore in Vertebrates would in no way oblige 
us to derive them with GROBBEN (1908) from the Deuterostomia, as 
