112 Phenomena Refuting Simple Epigenesis 
But the preformationists on their side cite certain partic- 
ular cases of regeneration as unfavorable to epigenesis: 
“Regeneration” remarks Roux, “takes place in tritons 
when all four extremities are removed at one time, from 
which it follows that for the formation of new extremities 
in one antimere, the presence of the other extremities 
is not in the least necessary, so that for this formation 
it is not necessary that there be any formative correlating 
influence extended from them.” ™4 
The anachronisms of development in which, for 
instance, certain parts remain behind other parts in their 
formation, or in which the germ layers may even develop 
with uneven speed, or one entire half of the body may 
take a jump ahead of the other half so that one can 
sometimes observe two different degrees of development 
in the two halves of the same embryo, belong likewise 
‘to the number of phenomena which simple epigenesis is 
incapable of explaining: “How the (epigenetic) con- 
ceptions of O. Hertwig,” Roux writes further,—and his 
words, already quoted above, deserve to be repeated here, 
—‘‘can be reconciled with these anachronisms in the 
development of the germ layers which I have observed, 
or indeed with the absence of the lower layer—the endo- 
blast (Anentoblastia), while both of the other two layers 
remain essentially normal in the disposition of their 
parts, or finally with the formation of half embryos, may 
well be left to the reader’s own judgment. For if such 
large parts can remain behind in their development, or 
indeed be lacking altogether, and the other parts be in 
no wise disturbed thereby in their development, it surely 
follows that the development of these latter is not con- 
“Wilhelm Roux: Uber Mosaikarbeit etc. Anat. Hefte, Febr. 
1893, P. 299. Gesamm. Abhand. II, P. 830. 
