360 H. H. Newman and J. T. Patterson. 



I. INTRODUCTION 

 A. Review of the Literature 



It is not our present purpose to attempt any comprehensive 

 review of the literature dealing with the development of the 

 Edentata, nor even of that treating especially of the armadillos. 

 It seems advisable, rather, to limit our survey to those contri- 

 butions, a knowledge of which is essential to an understanding 

 of the problem of specific polyembryony. 



That certain species of armadillos bring forth at a birth young 

 all of one sex has been known for over a century. According 

 to Azara, 2 a writer of the eighteenth century, the natives of 

 Paraguay and of the Argentine Republic knew that this was true 

 for the Mulita (Tatu hybridum). Any observant hunter, who 

 had been fortunate enough to capture a litter or two of young 

 animals in a burrow with the mother, might readily have noted such 

 a unique state of affairs, for the sexes are easily distinguishable. 



In the latter part of the nineteenth century Herman von Jher- 

 ing, ('85 and '86), met with similar statements on the part of 

 the natives of Brazil and was sufficiently interested to attempt 

 a scientific confirmation of what had been until then merely an 

 interesting piece of folklore. Two pregnant females came under 

 his observation, the uterus of each of which contained eight male 

 foetuses, all in exactly the same stage of development. Each 

 foetus was described as having its own separate amnion: but all 

 were surrounded by a common chorion. 



These conditions were interpreted in a* subsequent paper by 

 the same author as indicating the origin of the several embryos 

 from a single fertilized egg, and it was further assumed from the 

 facts in hand that the splitting of the original single germ into 

 separate embryonic primordia occurred at some period after 

 fertilization. Von Jhering apparently saw nothing more funda- 

 mental in this situation than' the discovery of a new type of ani- 

 mal reproduction to which he gave the name "temnogenesis." 

 Its bearings on the problems of sex determination and of heredity 



2 Referred to by von Jhering. 



