406 ANNUAL REPORT SMITH SONTA>T INSTITUTION, 1913. 



This is one of the reasons why the observance of traits from heredity 

 is so difficult. They are complicated by the intervening of such 

 numerous disturbing elements that the laws of heredity can be estab- 

 lished only by experimenting on some cases simplified as much as 

 possible. That is what Mendel has done. Before showing you the 

 very simple and suggestive laws discovered by Mendel, I ought to tell 

 you in a Avord the work of the investigators who preceded him. 



Naturally, I can give you only a brief and necessarily incomplete 

 sketch of this history. 



About the middle of the last century there were man}'' students 

 engaged in researches on heredity. Lucas published (1850) a book 

 entitled " De I'heredite " (On Heredity), in which he showed that the 

 condition of the descendant results from the combination of two 

 factors: (IJ "Heredity," which brings about a resemblance between 

 the subject and its parents and ancestors; (2) " inneite " (inherent), 

 causing a dissimilarity. Thanks to the innate idea, we see in some 

 families certain members who show no characteristic peculiar to the 

 famil}^ We now know that that theory is based on some deceitful 

 appearances explicable by disturbing causes of which I have given 

 you an example. The doctrine of Lucas has been forgotten by savants 

 for a long time. If I have spoken to you about it, it is as a contem- 

 poraneous writer. Emile Zola has based upon it that great work of 

 the Rougon-Macquart ; he has sought thus to give it a scientific 

 foundation ; the unfortunate part is that before Zola had even com- 

 menced the publication of the first volume of that set of books other 

 authoritative articles had already brought out the weak and inac- 

 curate points of Lucas's theory. 



A gTeat English investigator, Sir Francis Galton, has employed, 

 like Lucas, the direct method of observation in the study of acts of 

 heredity. He has carried it to a very high degi'ee of perfection. 

 Thanks to some devoted cooperators, he has united a large number 

 of genealogical trees in noting the physical, intellectual, and moral 

 characteristics of all members in the family studied. A periodical 

 work, " Biometrika," published these articles. The results were 

 worked out in a special laboratory which is perpetuated under the 

 name of the Sir Francis Galton Eugenic Laboratory. In applying to 

 results thus accumulated the process of higher mathematics, Sir 

 Galton and his pupils have established an empiric law, the formula 

 of which, however, has changed. At first Galton showed that the 

 two ancestors of the first generation (father and mother) control 

 one-half in the heredity of a subject, each one being a quarter; then 

 the four ancestors of the second generation (grandparents) are 

 valued at a quarter in this heredity, one-sixth for each one ; then the 

 eight ancestors of the third generation (gi-eat-grandparents) come in 

 for an eighth or a sixty-fourth for each one, etc Subsequently, 



