144 THE QUANTITATIVE METHOD IN BIOLOGY 



SECOND REMARK : The number of sorts of seeds (F, 

 generation) which the plants raised from any of the 27 grouns 

 may bear is indicated by the coefficient of the corresponding 

 term. According to this— ^ * 



Each of the 8 terms with coefficient i will yield i sort of 

 seeds ; total frequency 8 : 64. 



Each of the 12 terms with coefficient 2 wiU yield 2 sorts of 

 seeds ; total frequency 24 : 64. 



Each of the 6 terms with coefficient 4 wDl yield 4 sorts of 

 seeds ; total frequency 24 : 64. 



The term with coefficient 8 will yield 8 sorts of seeds- 

 frequency 8 : 64. 



In MENDEL'S experiment 639 F^ plants fruited and there 

 were among them — 



Plants yielding i sort of seeds . 

 „ 2 sorts of seeds . 



Observed 



n 

 228 



256 



78 



Calculated 



639 X -57= 80 



639 >^ It = 240 

 639xfr = 240 



639>«^= 80 



THIRD REMARK : The coefficient of each term indicates 

 in how many ways the corresponding seeds have been pro- 

 duced. Examfles: The seeds A^B'^C'^ are produced in one 

 way: ABC $ x ABC $ . The seeds ^AaBhC^ are produced in 

 fourways: ABC $ ^abC^.abC $ x ABC ^.AbC $ xaBC $, 

 aBC t xAbC ?. Etc. 



§ 107.— THE METHOD OF QUETELET FOR THE 

 MEASUREMENT OF THE VARIABLE PROPERTIES OF 

 LIVING BEINGS. MEAN VALUE.— In § 32 I have briefly 

 expounded the method initiated by QUETELET for the 

 measurement of the variable properties of animals and 

 plants. 



This method is based upon the principle that the variation 

 of a given primordium within the limits of a given species de- 

 pends on chance (variable combined cause) and is therefore 

 governed by the rules of probability (frequency). QUETELET 

 and his followers measure a given primordium in a large number 

 of specimens of the same species (§ 32) ; they construct the 

 variation curve and calculate the mean value. 



I think that the importance of the latter has been exagger- 

 ated. Before I expatiate on this subject I am going to expound 

 briefly, by means of examples, the way in which the method of 

 QUETELET is used for the measurement of the properties of 

 inanimate objects— in general, for the determination of magni- 

 tudes (constants, etc.), in inorganic nature. 



