linguistic:paraphrasing
Empirical test of pangenesis and Lamarckism

Galton conducted wide-ranging inquiries into heredity which led him to challenge Charles Darwin's hypothesis of pangenesis. Darwin had proposed as part of this model that certain particles, which he called " gemmules " moved throughout the body and were also responsible for the inheritance of acquired characteristics. Galton, in consultation with Darwin, set out to see if they were transported in the blood. In a long series of experiments in 1869 to 1871, he transfused the blood between dissimilar breeds of rabbits, and examined the features of their offspring. He found no evidence of characters transmitted in the transfused blood.

Darwin challenged the validity of Galton's experiment, giving his reasons in an article published in Nature where he wrote:

Now, in the chapter on Pangenesis in my Variation of Animals and Plants under Domestication I have not said one word about the blood, or about any fluid proper to any circulating system. It is, indeed, obvious that the presence of gemmules in the blood can form no necessary part of my hypothesis; for I refer in illustration of it to the lowest animals, such as the Protozoa, which do not possess blood or any vessels; and I refer to plants in which the fluid, when present in the vessels, cannot be considered as true blood. The fundamental laws of growth, reproduction, inheritance, &c., are so closely similar throughout the whole organic kingdom, that the means by which the gemmules (assuming for the moment their existence) are diffused through the body, would probably be the same in all beings; therefore the means can hardly be diffusion through the blood. Nevertheless, when I first heard of Mr. Galton's experiments, I did not sufficiently reflect on the subject, and saw not the difficulty of believing in the presence of gemmules in the blood.

Galton explicitly rejected the idea of the inheritance of acquired characteristics (Lamarckism), and was an early proponent of "hard heredity" through selection alone. He came close to rediscovering Mendel's particulate theory of inheritance, but was prevented from making the final breakthrough in this regard because of his focus on continuous, rather than discrete, traits (now regarded as polygenic traits). He went on to found the biometric approach to the study of heredity, distinguished by its use of statistical techniques to study continuous traits and population-scale aspects of heredity.

This approach was later taken up enthusiastically by Karl Pearson and W. F. R. Weldon; together, they founded the highly influential journal Biometrika in 1901. (R. A. Fisher would later show how the biometrical approach could be reconciled with the Mendelian approach.) The statistical techniques that Galton developed (correlation and regression—see below) and phenomena he established (regression to the mean) formed the basis of the biometric approach and are now essential tools in all social sciences.