640 J. T. PATTERSON 



amniotic vesicle. Curiously enough it is found in two or three 

 instances that the canals of two embryos unite and enter the vesi- 

 cle as a single tube, and in one case at least three canals so unite. 

 His figure 2 presents a still more striking case. It contains 9 em- 

 bryos, and the embryo lying at the top of the figure, and slightly 

 to the right of the center, sends its canal directly to the vesicle, 

 while the canals from the four embryos on the right enter the vesi- 

 cle very close together, two of them by a common tube. Like- 

 wise, the canals from the four embryos lying on the left enter the 

 vesicle at a common point. Indeed, they apparently unite just 

 before reaching the vesicle. 



In view of the fact that we have shown that the union of two 

 canals in T. novemcincta is a certain indication of their common 

 origin from a primary bud, I believe we are justified in drawing a 

 similar conclusion from the conditions to which we have just 

 called attention "in T. hybrida. And I venture to predict that 

 when Fernandez shall have secured intermediate stages, he will be 

 able to confirm this conclusion. 13 



It does not follow, of course, that in Mulita only two primary 

 buds will be found -to appear, for while in T. novencincta the poly- 

 embryonic process in the ovum is* extremely stable, as expressed 

 by the constancy with which litters of quadruplets appear, in T. 

 hybrida, on the contrary, variability characterizes this process. 

 Hence, there are no good reasons why in this species, regions on 

 the ectodermal vesicle which correspond to those unoccupied by 

 the two primary buds in the vesicle of novemcincta might not 

 give rise to new primary diver ticula. If this be found to be the 

 the case it would in no wise nullify our conclusion regarding the 

 origin of polyembryony among the armadillos; that is that it 

 began in the ancestors by the formation of twins. Whether all 

 of the species which might show such a primitive condition are 



13 After the above was written my attention was called to a report, in the Jour- 

 nal of the Royal Microscopical Society, June 1913, page 279, of Fernandez's commu- 

 nication at the Ninth International Congress of Zoologists. From the brief state- 

 ment given it seems clear that Fernandez has observed exactly the same method of 

 embryo formation in Mulita that I have described for T. novemcincta, that is, the 

 embryonic primordia arise as diverticula. He states that the diverticula "become 

 the primordia of embryos, either directly or after division.'' (Italics my own). 



