860 H. H. NEWMAN AND J. THOMAS PATTERSON 
that even their best friends confuse them.’ It must be confessed, how- 
ever, that the differences in the formulae cannot be reconciled, and that 
the palms are, and remain, in respect to the main lines, very different. 
*In the light of the results presented below we are inclined to 
believe that Wilder was not justified in thus arbitrarily exclud- 
ing from the category of ‘duplicates’ such cases as those referred 
to, for we have found not a few sets of armadillo foetuses which 
exhibit greater differences than some of Wilder’s so-called ‘fra- 
ternals.’ Hence, although the results of his studies are valuable 
and highly suggestive, they are insecurely founded and therefore 
cannot be applied to the solution of the problem of the limits of 
hereditary control. 
The material which forms the basis of the present investigation 
consists of a collection of advanced sets of foetuses (removed 
from the uterus with all of their placental connections intact) of 
a species of mammal, Tatu novemcinctum, in which we have 
demonstrated conclusively the existence of specific polyembryony ; 
and hence all sets of embryos, whether strikingly similar or not, 
are known to be the product of the division of a single fertilized 
egg. The basic assumption involved in the case of human dupli- 
cate twins is thus obviated, and at the same time it is possible 
to eliminate the factor of a diverse post-natal environmental 
experience by examining unborn foetuses, whose inter-relation- 
ships are shown by their placental connections. In the scutes 
of the banded region we have characters little if at all subject, 
even during gestation, to environmental control. We plan in 
the present paper to present an intensive study of the phenomena 
of blastogenic variation as exhibited by these integumentary 
elements, limiting our present investigations to the well defined 
banded region, believing that the conclusions arrived at from the 
study of one region will prove to be generally applicable, and that 
what is true for one character or set of characters will be found 
to apply in a general way to the whole organism. 
In order that there may be no misunderstanding as to the kind 
of variates we are dealing with, it seems advisable to present in 
abbreviated form the results of a study of the morphology of the 
integument and of the variability of its elements as exhibited by 
