160 
yet a little further (fig. 44 b), a secondary relation between 
neurenteric pore (blastopore) and anus results *) The anus 
now opens to the exterior through the hindmost extremity 
of the medullary tube. From the medullary canal there isa 
passage through the anus to the exterior as well as through 
the neurenteiic pore into the archenteron, and from the 
archenteron through the neurenteric pore and the anus to the 
exterior. In ontogeny this will result in the non closing of the 
medullary folds over the rear end of the slit-like blastopore, 
and in the leaving of an opening, viz. the anus. Possibly 
they will develop slightly at both sides of the rear part of 
the blastopore under the influence of the formation of the 
b. 
Fig. 44. (cf. fig. 11, p. 220). Diagram of the relation between anus 
and blastopore, and of the tail-forming. 
a at the moment of the closure of the neural folds is Anurans, 
Urodelans, 
Ee 6 he se chians, 
at the same time representing the growing out of the tail 
in Amphibians. 
a anus, p.n. neurenteric pore; the entoderm is dotted. 
anus at this point, or possibly not. If we imagine things 
very much enlarged and if we look through the anus into 
5) In a longitudinal section as in fig. 44 the conditions at first 
sight might appear in fig. 44 b radically different to those in , 
In an elevation, however, the agreement between them will be evident. 
