BLASTOGENIC VARIATIONS. 137 



whilst a heterogeneity of material, such as a mixture 

 of two different local races, would tend, as a rule, to 

 raise correlation.* Also the environmental factor, and 

 the difficulty of ensuring that all individuals are of the 

 same age, or in the same state of development, must be 

 borne in mind. 



Professor Pearson therefore considers that he is 

 justified in assuming that the intensity of pure homo- 

 typosis throughout the vegetable kingdom probably 

 lies between A and .5, and as this is the mean value for 

 fraternal correlation, he believes that " heredity is 

 really only a phase of the wider factor of homotyposis." 



In a criticism of Pearson's conclusions, Bateson f 

 draws attention to the fact that it is difficult or impos- 

 sible to distinguish between chance variation occurring 

 between members of a series, and actual differentiation, 

 which may be present in greater or less degree. He 

 therefore considers that the average value of the homo- 

 typosis coefficient has no significance. However, Pear- 

 son states that the " diversity due to differentiation. . . 

 is the result of dominating factors which can be isolated 

 and described," though he does not attempt this in 

 detail in his present memoir. To what extent he will 

 be able to accomplish it, and so ultimately obtain the 

 true correlation constants of absolutely undifferentiated 

 like organs, remains to be seen.J 



*Z. c.,p. 292. 



fProc. Roy. Soc., Ixix. p. 193. 



t See also rejoinder by Professor Pearson in Biometrika, i. p. 

 320, 1902. 



