402 H. H. Newman and J. T. Patterson. 



would mean that sex is determined by certain conditions in the 

 egg. With only three cases in hand a discussion of the matter 

 would be unprofitable. 



In two cases out of three it was possible to enumerate the scutes 

 in the nine bands of armor and on that basis to determine the 

 varying degrees of resemblance among the embryos. 



The occurrence of five embryos involves a decided asymmetry 

 of the placental and amniotic elements and an atypical arrange- 

 ment of the embryos. In each case the condition of two main 

 lateral discs was maintained, but one of these discs, the one to 

 which three embryos were attached, was considerably larger than 

 the other. An examination of the larger disc shows that in each 

 case it is composed of only two, not three, primary discs. One 

 of the primary discs, on the side where three embryos are attached, 

 is twice the normal size and to it are attached in symmetrical 

 fashion the umbilical cords of two embryos. Apparently there is 

 no regularity about the position of the double disc. In one case 

 the double disc is ventral, and in the other two right lateral in 

 position. Believing that the two embryos attached to a single 

 primary disc are the equivalent of one typical embryo, we shall 

 give them the same number, as for example, I and I'. 



The following conditions are found in vesicle 91, the relative 

 positions of the embryos being indicated in the diagram of the 

 placenta, represented as cut open along the narrow dorsal bridge 

 and laid out flat (fig. 5) . The number of scutes in the nine bands 

 of armor are indicated on the figure. It will be noted that there is 

 distinct pairing on the normal side of the vesicle, between em- 

 bryos III and IV; that the resemblance between the two embryos 

 on the large disc (I and I') is equally close; but that there is a 

 wide difference bewteen these two embryos and the single embryo 

 on the same side (no. II). 



In vesicle 108 somewhat similar conditions exist, but the vesi- 

 cle is laid open along the ventral bridge (fig. 6). Embryos II and 

 II', having a common primary placental disc, are identical in the 

 number of scutes but widely different from embryo I, which is 

 attached to the other primary disc on the same side of the vesicle. 

 Embryos III and IV are quite different from those on the other 

 side, but are fairly similar to each other. 



