5° 



THE BIOLOGY OF TWINS 



the typical number of embryos in that species ranges 

 from seven to twelve. An inspection of Fig. 15 leads 

 one to a different interpretation of the relation of 



Fig. 14. — Armadillo egg showing two out of four embryos growing 

 away from the common amnion (c am). The other two embryos 

 (I and III) do not show in this plate. A view from the lower pole of 

 the egg is seen in Fig. ij. (For description see stage VII.) 



secondary to primary embryonic primordia from that 

 offered by Patterson. I am inclined to beUeve that 

 prior to the visible formation of outgrowths the ecto- 



