638 J. T. PATTERSON 
bud, either directly, through the formation of three secondary 
buds from it, or through a further division of one of the two 
secondary buds, after they had been formed in the normal way. 
It is to be regretted that the rare case of a two-embryo set, 
referred to above, was not studied before birth occurred, as it 
would doubtless have been found that the embryos occupied the 
right and left sides of the chorionic vesicle, thus indicating that 
each primary bud had been directly transformed into a single 
individual. In that event, we should have had very strong evi- 
dence in support of our contention that specific polyembryony in 
the Dasypodidae began by the formation of a set of twins, per- 
haps at first as sporadic cases of gemelliparous development such 
as probably occurs in the production of duplicate twins in the 
human species. 
However that may be, I have recently descovered certain evi- 
dence in the early development of the Texas armadillo which 
strongly supports this view concerning the origin of specific poly- 
embryony in the Dasypodidae. It was pointed out in an earlier 
section that when the secondary buds first appear, Nos. II and 
IV apparently arise from the tips of the primary buds, as though 
they were merely prolongations of these buds; while each of the 
other secondary buds evidently arises slightly to one side of tip 
of aprimary bud. That is to say, that Embryo I always arises 
to the left of its paired mate No. ITI, and likewise Embryo III to 
the left of IV (fig. 2). This may be expressed in another way 
by saying that buds I and III are outgrowths from the primary 
buds, and that consequently they follow chronologically the 
development of buds II and IV. The evidence upon which this 
interpretation is based is to be seen in several of the young 
blastocysts. 
It has been pointed out elsewhere that the first sign of a secon- 
dary bud appears on the right side of the left-hand primary bud 
in blastocyst No. 247 (fig. 1). The other embryonic bud is the 
result of a prolongation of the extreme tip of the primary diver- 
ticulum. In figures 2, 3, 4, and 28 is seen further evidence of 
this same difference in the size of the two members of a pair of 
embryos, and it is also evident in the sections (figs. 67, 77). 
