450 THE GRAMMAR OF SCIENCE 



tree, so there is variability among the offspring of a 

 parthenogenetic mother, and of course still more variability 

 among the offspring of a sexual union.^ It is an error to 

 suppose that there is no variation in the undifferentiated 

 like organs put forth by a single individual, there is a 

 perfectly definite variability and this can be ascertained 

 and quantitatively described. What we may term the 

 " adult " blood corpuscles of an animal, say a frog, are 

 neither of the same size nor the same shape ; they vary 

 also from frog to frog ; thus they have an individual 

 type and a race type (see p. 381). Now if we consider 

 sexual reproduction, we find the male individual producing 

 a number of male reproductive cells, the male gametes, and 

 the female individual a number of somewhat different 

 reproductive cells, the female gametes. Each individual 

 gives a group of gametes of a given individual type and 

 given individual variability. The conjugation of two 

 gametes, male and female, gives what has been termed the 

 zygote or stirp, the origin of a new individual. Every zygote 

 produced by the conjugation of gametes taken from the 

 same male and female groups is not alike. A group of 

 offspring from the same parents are not alike, because the 

 conjugating gametes are taken, let us assume for the 

 present at random, from two groups, all members in either 

 of which are not alike. The variability among brethren 

 is thus seen as a direct corollary to the law according to 

 which any individual puts forth a group of undifferentiated 

 like organs (p. 403). The investigation of the relation 

 between the law of individual growth and the variability 

 of brethren is too complex to be given here, but the point 

 to be insisted upon is this : the resemblance between 

 brethren, or indeed, any pair of relatives, is a consequence 

 of the resemblance, that is the degree of correlation, 

 between undifferentiated like organs in the individual. 

 Allow for environment, allow for growth, and yet the like 

 parts of an individual are not~ identical. What is the 



1 The quantitatively exact expressions for all these variabilities and their 

 inter-relationship have been obtained. It is a completely erroneous view which 

 suggests that all variation is due to conjugation. 



