22O HARRIS HAWTHORNE WILDER. 



In this animal the early stages are now quite fully known, ex- 

 cepting cleavage, and the first visible signs of multiple indi- 

 viduals are here seen in a process of budding of the embryonal 

 anlage. Almost spontaneously comes the impulse to attribute 

 the origin of human twins and other multiple births to a like 

 process, as was done by Patterson at the time of his discovery; 

 writing: "I am therefore bold enough to suggest that the con- 

 clusions which I have drawn concerning the origin of the embryos 

 in this mammal may also apply to cases of duplicate twins and 

 double monsters in the human species." To render this still 

 more plausible he then refers to certain similarities in the early 

 embryology of the two animals considered, man and the arma- 

 dillo, particularly as shown in the Bryce and Teacher embryo, 

 1908, a similarity which renders this process in man mechanically 

 possible. 



Although this conclusion may seem at first to place the origin 

 of these multiple individuals at the time the budding process is 

 first manifest, there is still much evidence to show that this 

 process rests upon an earlier process w T hich conditions it, that is, 

 that while the visible process of budding first reveals the multi- 

 plicity of individuals developing from the egg, the true cause is 

 to be sought further back, or, as Newman and Patterson, as well 

 as myself, stated at the beginning of our investigation, in some 

 sort of divison (or we may now say, differentiation) of the early 

 blastomeres. 



It is now clearly evident that all ideas of an actual physical 

 separation of these blastomeres, a definite blastotomy, does not 

 take place, yet many things still point to the conclusion that a 

 similar condition is obtained through some form of differentiation, 

 and that each of the separate embryonal anlages, be they two 

 or four or eight or eleven (a possible number in Tatusia hybrida), 

 is the lineal descendant of a single blastomere, formed during 

 early cleavage. This was the view of Newman and Patterson 

 in 1910, who then wrote: "It seems highly probable that the 

 tissues involved in each of the four quadrants of an embryonic 

 vesicle do really arise as the lineal descendants of one of the first 

 four blastomeres." They further believed, as they definitely 

 expressed farther on, that this differentiation was not a blastot- 



