CHAPTER III 



MODES OF TWINNING IN OTHER SPECIES 



OF ARMADILLO 



Before attempting a discussion of the probable 

 origin and causes of polyembryonic twinning in the 

 nine-banded armadillo it will be well to learn something 

 about the conditions known for other species of arma- 

 dillo. Nothing is more likely to furnish a clue to the 

 solution of the problems presented by one particular 

 species than a comparative study of the embryology of 

 allied forms. 



Previous references have been made to Fernandez' 

 account of the polyembryonic development of the 

 Mulita (Dasypus hyhridus). His account of stages 

 corresponding to those illustrated by our Figs. 12-19 

 are so nearly identical with those described in the last 

 chapter for D. novemcinctus that it will be unnecessary 

 to do more than indicate the somewhat minor differences 

 in detail. A comparison of Fernandez' figures (Figs. 23 

 and 24) with our Figs. 12 and 14 will indicate the close 

 similarity. 



The two species of Dasypus are evidently very 

 closely related, and it would appear probable that D. hy- 

 hridus is a comparatively recent derivative of D. novem- 

 cinctus. The only important particular in which a 

 difference exists is in the number of young in a poly- 

 embryonic litter. While in D. novemcinctus the number 

 is almost uniformly four, in D. hyhridus the number is 



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