An Introduction to a Biology 



divisions of the germ-cells, and the concomitant extrusion 

 and loss of one-half of the several contributions from each of 

 the two parents to the germ-cell of the offspring." Mark 

 his words, " . . . though with less precision in individual 

 cases " the italics are mine. If one were referring to 

 Galton's Law (in the form in which it is true of masses only) 

 one would say, "... without applying at all to individual 

 cases " ; and if to the Law of Contribution, "... with 

 absolute precision to individual cases." But I may be inter- 

 preting this wrongly, for the " less " may refer not to the 

 difference between population and individual, but to the 

 difference between person and germ. And, in fact, I think the 

 following quotation from the previous page ('97, p. 402) justifies 

 us in concluding that Galton conceived his Law 'as being 

 true solely of masses without being true of the component 

 individuals. " The neglect of individual prepotencies is 

 justified in a law that avowedly relates to average results . . ." 

 At any rate, it simplifies matters very much to consider 

 that Galton's Law as he formulated it is true of masses only, 

 and not of their component units ; for if we do not, we 

 have to keep three laws distinct in our minds : 



1. Galton's Law as he formulated it : true of masses, but 



also, though with less precision, of individuals. 

 Statistical and Physiological. 



2. Galton's Law : true of masses only. Statistical. 



3. The Law of Contribution : true of units. Physio- 



logical. 



APPENDIX B to p. 171 



There is nothing, of course, in the word " contribute " 

 to definitely signify that the thing which is contributed is 

 the same as that which contributes : in fact, in the every- 

 day usage of the term this is hardly ever the case. But it 

 is reasonable to hold that Galton's Law is the generalisation 

 that like contributes like and not unlike ; and it is certain 

 that Galton himself meant this, as the last words of his 

 illustration of particulate inheritance readily show : ". . . each 

 piece of the new structure is derived from a corresponding 

 piece of some older one, as a lintel derived from a lintel, 

 a column from a column, a piece of wall from a piece of 

 wall." ('89, p. 8.) 



197 



