22 



COAT CHARACTERS IN GUINEA-PIGS AND RABBITS. 



He gives a series of his own and that of Galton in comparable form. 

 They are, he says, " if we measure parental influence by intensity of 

 correlation " : 



Even when they are given thus, it seems to me still, as I stated 

 before, that " Pearson attaches more weight to the remoter ancestors 

 than does Galton," and if so, that " the discrepancies noted between 

 observed and calculated [in testing Galton's law] will remain and even 

 be accentuated if we replace Galton's series with one of those suggested 

 by Pearson." That Pearson himself had not contemplated such a test 

 of his law would not affect in the slightest degree the outcome of the 

 test. Further, it seems to me an admission very damaging to a law of 

 heredity when Pearson says : " Personally I have no means of deter- 

 mining whether the law of ancestral heredity holds or does not hold for 

 coat color in mice. The theory has not yet been worked out in a form 

 covering Von Guaita's cases." Yet in Von Guaita's material we have 

 a full record of the coat color of every animal in seven successive gen- 

 erations, and we know that back of this for an indefinite number of 

 generations all the ancestors on one side of the ancestry were albinos, 

 on the other side spotted black-and-white. That is sufficient basis on 

 which to make very reliable predictions as to the character of the off- 

 spring, under Mendel's law, as I have elsewhere shown. 



In fact, it seems to me that Pearson's law, as he now explains it, is 

 not a law of heredity at all, but one of variability in successive gen- 

 erations, for he says (p. no) : " So far as I can understand the Law of 

 Ancestral Heredity as I have myself enunciated it, the produce of a 

 grey mouse and a fawn mouse might be on the average a green mouse 

 without that Law having anything to say on the point. From it you 

 can not possibly deduce what number of the offspring of any generation 

 will be like this or that ancestor. It is not a law of types, but of the 

 distribution of deviations from type, and this is a very different thing 

 indeed." But from a genuine law of heredity, such as that of Mendel, 

 one is enabled, as I have shown, to predict with great accuracy what 

 color types will prevail among the offspring in successive generations. 

 Since Pearson's law, as now interpreted by its author, though dealing 

 with alternative color types in successive generations, gives no informa- 



