PALM AND SOLE STUDIES. 221 



omy in the sense of anything involving a separation, and sup- 

 posed that even if an embryo were found in the 4-cell stage, it 

 would present to the eye no differences from that of any other 

 mammalian embryo of four cells. The exact truth of this sup- 

 position can be known only by a thorough knowledge of the cell- 

 lineage, from the fertilized egg up to the beginning of the budding 

 process, and although such a task is well-nigh inconceivable 

 with our present technique, the results already obtained render 

 even this possible in the future, perhaps by a culture of eggs 

 outside of the body of the mother. 



In 1913, after his important studies of the early embryology 

 of the armadillo, Patterson seems to diverge a little from this 

 view of so early a differentiation, and seems almost to confuse this 

 with blastotomy, or at least to feel that blastotomy is necessarily 

 involved in the process, for he says: "The evidence that has been 

 presented in the first part of this paper [describing the budding 

 process] makes it certain that polyembryonic development in the 

 armadillo cannot be explained on the basis of a spontaneous blas- 

 totomy, in the sense that each embryo is the lineal descendant of a 

 single blastomere of the four-celled stage, and it causes me to view 

 with some doubt the conclusions of this same nature that have 

 been drawn by those who have worked on other polyembryonic 

 forms." The italics are my own, as I wish to call attention to 

 what seems to be his interpretation of blastotomy, whereas the 

 two things, (i) a separation of the blastomeres, and (2) a line of 

 cell lineage which causes the separate anlages to develop each 

 as the descendant of one of them, are not at all the same, and have 

 no necessary connection. The passage is a little obscure, and the 

 author may not mean to express my interpretation, but it cer- 

 tainly seems as though he has abandoned any connection between 

 the numerous embryos and the first four cells, and considers that 

 the separate individuality commences with the budding process 

 very much later. Whatever may be this author's opinion on 

 this subject, which is very likely not as inferred from this sen- 

 tence, it would seem to me impossible to get such a close corre- 

 spondence as has been shown in the armadillo, and in human 

 twins, without starting the separation of identities before there 

 has been any appreciable differentiation in the material that 



