642 J. T. PATTERSON 
As to the origin of duplicate twins, Wilder advocates the 
blastotomy theory, believing that it is the result of a total sepa- 
ration of the first two blastomeres of the single egg. In case the 
blastomeres fail to separate completely, symmetrical double 
monsters (dislopagi) result. In this connection he says, “The 
double monsters of which we have authentic record are sufficiently 
numerous and diverse to represent every stage from that of the 
otherwise normal individual with a doubling of certain of the 
median parts, to that of two complete duplicate twins with a 
slight connection between them.’ Finally, be believes that 
unequal duplicate monsters (autosite and parasite) are the result. 
of a secondary fusion (due to the great contiguity) of two embryos 
which were at first duplicate twins. 
The contention that duplicate twins and double monsters arise 
from a single egg is undoubtedly sound, but the conclusion that 
their origin is the result of a complete or a partial separation of the 
first two blastomeres, is, I believe, open to question. However, 
in the absence of any study in the early stages of these sporadic 
cases of polyembryony, and in view of the results from experiments 
on artificial blastotomy, this conclusion seemed both natural 
and logical. In the study of the embryology of the armadillo we 
have a most excellent opportunity to put the blastotomy theory 
to test; for here is a mammal with a simplex type of uterus, and 
one which habitually reproduces by polyembryony. I am_there- 
fore bold enough to suggest that the conclusions which J have 
drawn concerning the origin of the embryos in this mammal may 
also apply to cases of duplicate twins and double monsters in the 
human species. And I am encouraged to make this suggestion be- 
cause of the recent discoveries in the human ovum (e. g. the Bryce 
and Teacher ovum, ’08), in which the condition of the ectodermal 
vesicle is shown to be such as to require no great stretch of the 
imagination to picture how diverticula might arise from it, and 
thus initiate the development of two or more embryos. Nor is 
there any greater mental strain in accounting for the origin of 
composite monsters in this way than is required in the hypothet- 
1 Locs (cit: p. 462. 
s . 
