364 H. H. Newman and J. T. Patterson. 



fertilized females. Although we fully expect to secure the earliest 

 stages in the course of time it seems inadvisable for us to post- 

 pone the publication of the results thus far obtained, results suffi- 

 ciently clean cut in themselves to form the basis of a self-consis- 

 tent and fairly well rounded embryological account. 



At present we have in our possession seventy embryonic vesicles 

 comprising a close series of stages ranging from the primitive streak 

 stage to birth. 



Little need be said about the methods employed. To each ani- 

 mal that reached the laboratory was given a number and a page 

 in a ledger where all facts that might be of interest were recorded. 

 In case the carcase was to be thrown away complete records of 

 all data that might be useful in the future were kept. The ovaries 

 of the majority of the females were fixed in the standard cytologi- 

 cal fluids. Every^art taken from a given specimen was numbered 

 accordingly. Much of the data thus gathered proved useful 

 during the course of the work and we have no doubt that all of it 

 will ultimately serve to throw light on future investigations. 



C. Pur-pose and Scope of the Present Paper 



In this our second contribution to the developmental history of 

 the armadillos the main purpose in view is to establish the fact of 

 specific polyembryony and thus to clear the way for future in- 

 vestigation. A more or less tentative explanation of its causes 

 and of the conditions and relations that result from it is hazarded 

 on the strength of the evidence now in hand, which is internal in 

 contradistinction to that derived from an examination of the ovar- 

 ies and testes, no detailed discussion of which is attempted at 

 present. 



Although the question of polyembryony is the central problem 

 it is impossible to treat of it as an isolated phenomenon for the 

 reason that many curious developmental processes are intimately 

 associa ted with i t . The history of the amnion and of the placenta, 

 for example, would be indecipherable apart from the fact of poly- 

 embryony, and the inter-relationships of the embryos admit of 

 a rational explanation on no other basis. The associated phenome- 



