2 



Prof. Karl Pearson, and others. 



of heredity we speak of the degree of resemblance as the fraternal 

 correlation, while the intensity of the diversity is measured by the 

 standard deviation of the array of offspring due to given parents. 

 Both correlation and standard deviation are determined for any given 

 character or organ by perfectly definite well-known statistical methods. 

 Passing from the case of bi-parental to asexual reproduction, we may still 

 determine the correlation and variability of the offspring. This ulti- 

 mately leads us to the measurement of the diversity and likeness of 

 the products of pure budding, or, going still one stage further, we 

 look, not to the reproduction of new individuals, but to the production 

 of any series of like organs by an individual. Accordingly one reaches 

 the following problem : — If an individual produces a number of like 

 organs, which so far as we can ascertain are not differentiated, what is 

 the degrees of diversity and of likeness among them 1 Such organs 

 may be blood-corpuscles, hairs, scales, spermatozoa, ova, buds, leaves, 

 flowers, seed-vessels, &c, &c. Such organs I term homotypes when 

 there is no trace to be found between one and another of differentiation 

 in function. The problem which then arises is this : — Is there a 

 greater degree of resemblance between homotypes from the same 

 individual than between homotypes frOm separate individuals ? If fifty 

 leaves are gathered at random from the same tree and from twenty- 

 five different trees, shall we be able to determine from an examination 

 of them what has been their probable source ? Are homotypes from 

 the individual only, a random sampling, as it were, of the homotypes of 

 the race % 



By the examination of very few series from the animal and 

 vegetable kingdoms I soon reached the result, that homotypes, like 

 brothers, have a certain degree of resemblance and a certain degree 

 of diversity ; that undifferentiated like organs, when produced by the 

 same individual, are, like types cast from the same mould, more 

 alike than those cast by another mould, but yet not absolutely identi- 

 cal. I term this principle of the likeness and diversity of homotypes 

 homotyposis. It soon became clear to me that this principle of homo- 

 typosis is very fundamental in nature. It must in some manner- 

 be the source of heredity. It does not, of course, " explain " 

 heredity, but it shows heredity as a phase of a much wider process 

 — the production by the individual of a series of undifferentiated-like 

 organs with a certain degree of likeness. My first few series 

 seemed to show that the homotyposis of the vegetable and animal 

 kingdoms had approximately the same value, and it occurred to me 

 that we had here the foundation of a very widespread natural law. 

 In order to demonstrate its truth, however, the homotyposis of a large 

 range of characters in a great number of species must be investigated, 

 and I soon found my own unaided efforts were quite unequal to the 

 task of collecting, tabulating, and reducing the data. As the 



