Bauhaus-Universität Weimar

The Development of the Nine-banded Armadillo from the Primitive Streak Stage To Birth; With Especial Reference to the Question of Specific Polyembryony
Newman, H. H. Patterson
H. H. Newman and J. T. Patterson. 
4. The fact that all of the embryos of a set are invariably of the 
same sex strongly suggests their origin from a single fertilized egg. 
5. The definite orientation of the embryos in the vesicle, and 
of the vesicle in the uterus, precludes the possibility of their origin 
from several eggs, even though these might conceivably be simul¬ 
taneously given off from the ovary. 
6. The inversion of germ layers presents a condition in both 
Tatu hybridum and in T. novemcinctum, which could not be at¬ 
tained by the union of several eggs to form a single vesicle. This 
is the strongest piece of evidence for specific polyembryony that 
has been advanced, and, to our minds, is practically conclusive. 
7. The Träger orprimitiveplacenta, common to all four embryos, 
is the morphological equivalent of that seen in the monembryonic 
vesicles of certain rodents. 
8. The overgrowing fringe of arborescent villi seen in middle 
stages of gestation reminds one strongly of the cricoid placenta 
seen in the monembryonic vesicle of the six-banded armadillo, 
figured by Chapman. 
9. The existence of partial or rudimentary embryos is evidence 
against the idea that the several embryos have been derived from 
separate eggs, for it is difficult to understand why some should 
develop perfectly, while others, under the same environmental 
conditions, should have so little success. 
10. The pairing of embryos points to the origin of each pair 
from one of the first two blastomeres. 
11. The presence of an accessory chromosome in the male germ 
cells suggests that the spermatozoon is the sex determiner. On 
this basis the fertilization of several eggs always by the same kind 
of spermatozoa seems highly improbable.


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