206 THE SOCIAL LIFE OF ANIMALS 



ognized differences either in the handling of the 

 children, in their early contacts with each other, or 

 in their impacts with their physical environment 

 which may have been cumulative enough to pro- 

 duce these social differences. It is also possible, as 

 Professor H. H. Newman suggests, that the differ- 

 ences are environmental after all. We must remem- 

 ber that from the standpoint of A, C, Y, M, and E, 

 their environmental relations began long before 

 birth, and though the care given them since birth 

 may have been practically identical in each case, it 

 may not have been possible to erase environmental 

 conditions impressed upon them during their seven 

 critical months of intra-uterine life. 



Whatever the reason, we have come to an inter- 

 esting, and, I think, important conclusion, which is 

 that animals with exactly the same heredity may 

 still develop, even at an early age, graded social dif- 

 ferences showing that one is not exactly equal to 

 the other. We have indications that the same prin- 

 ciple holds among birds, but even if present indica- 

 tions are finally borne out, the experiment will not 

 be as elegant, in the strictly scientific sense, as are 

 these observations on the Dionne quintuplets. 



Finally, by way of review, there exists among 

 flocks of birds, even though they may be identical 

 to the human eye, a graded series of reactions within 



