470 Mabel Bishop 



and that the embryonic arterial conditions in the Terata did not pass 

 from single to double dnring individual development, but unfolded them- 

 selves from the first in accordance with the diagrams given to explain 

 each case. 



(6) That starting from such a condition, each case was modified by 

 its ph3-siological necessities. 



(7) That it is possible, therefore, to conceive of these terata as repre- 

 senting progressive stages in a single series of "orderly living beings," 

 which begins with organisms less than a single individual and approaches 

 duplicate twins as the other limit, and includes between these limits 

 normal beings and creatures of more than one but less than two com- 

 plete individuals. 



(8) That such a cosmobiotic series is not confined to any one genus or 

 species, but is applicable to all vertebrates. 



In conclusion, I take pleasure in expressing my thanks to Dr. H. H. 

 Wilder, whose interest in the present research has been unceasing, and 

 whose practical suggestions and many kindnesses have been invaluable. 



Smith College, Northampton, Mass., 

 May 20, 1908. 



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