POLYEMBRYONIC DEVELOPMENT IN TATUSIA 615 
the pair of canals united at a very short distance from the 
vesicle, and thus entering it as a single short tube. Variations 
from this are seen in those cases in which the union takes place 
further and further away from the amniotic vesicle. In one of 
the most extreme cases observed the two canals on one side 
were united for a distance of about three millimeters from the 
vesicle, or more than half way between the anterior end of the 
embryo and the amniotic vesicle. 
Fig.5 A free hand drawing of specimen No. 276, in which the embryonic 
rudiments are well started. Each embryo is connected with the common amniotic 
vesicle (C.A.V.) by means of a slender tube-like canal. In the living condition 
the vesicle measured about 5 mm. high by 3 mm. at the widest point. X 11. 
The important point is that in all of these cases the paired 
condition of the embryos is unmistakably clear, and I know of 
no other way to account for this except to assume that it rests 
upon the manner in which the pair of secondary buds arises 
from the primary buds. If the secondary buds start soon after 
the primary buds are formed, than a condition similar to that 
seen in figure 5 might readily result; but if the primary bud has 
made considerable progress in its extension from the vesicle 
before the secondary buds arose from it, then we should expect 
