124 NATURAL INHERITANCE. [CHAP. 



accommodation. Evolution may produce an altogether 

 new type of vessel that shall be more efficient than the 

 old one, but when a particular type of vessel has become 

 adapted to its functions through long experience it is not 

 possible to produce a mere variety of its type that shall 

 have increased efficiency in some one particular without 

 detriment to the rest. So it is with animals. 



Variability in Fraternities. Human Fraternities are 



\j 



far too small to admit of their Q being satisfactorily 

 measured by the direct method. We are obliged to 

 have recourse to indirect methods, of which no less than 

 four are available. I shall apply each of them to both 

 the Special and to the E.F.F. data ; this will give 8 

 separate estimates of its value, which in the meantime 

 will be called 6. The four methods are as follow : 



First method ; by Fraternities each containing the 

 same number of persons : Let me begin by saying that 

 I had already found in the large Fraternities of Sweet 

 Peas, that the sizes of individuals of whom they con- 

 sisted were normally distributed, and that their Q was 

 independent of the size, or of the Stature as we may 

 phrase it, of the Mid-Fraternity. We have also seen 

 that the Q is practically the same in all Co-fraternities 

 of men. Therefore it is reasonable to expect that it 

 will also be found to be the same in all their Fraternities, 

 though owing to their small size we cannot assure our- 

 selves of the fact by direct evidence. We will assume 

 this to be the case for the present ; it will be seen that 

 the results justify the assumption. 



