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Mendel's Law of Heredity. 



By D. J. Scourfield, F.R.M.S. {Resume of Lecture delivered 

 November gt/i, 1905.) 



The important generalisation now known as " Mendel's Law of 

 Heredity " was published as long ago as 1865 by Gregor Mendel, an 

 inmate of the Augustine monastery at Briinn, in Austria, where for 

 about ten years previously he had carried on the experiments upon 

 which it was based. 



But his work was quite forgotten until 1900, when the rediscovery 

 of his paper was independently announced by three botanists — De 

 Vries, Correns, and Tschermak — who had been doing work of 

 somewhat the same character and obtaining very similar results. 



With the exception of a short paper on Hawkweed hybrids (1869) 

 Mendel did not publish anything further on the subject, and after 

 becoming Abbot of Briinn he does not seem to have had time to 

 continue his experiments, so that when he died, in 1884, his name 

 was practically unknown to science. It is not likely, however, that 

 it will be forgotten again. 



The most interesting way of approaching this subject will be to 

 briefly consider what Mendel did and the conclusions he drew from 

 his experiments. The task which he set himself was to follow up 

 the development of hybrids * in their progeny so as to be able to 

 determine the different forms under which they could appear and 

 their numerical relations. He recognised that to get intelligible 

 results in such an inquiry he must use suitable objects, and after 

 devoting some time to preliminary experimenting, he finally fixed 

 upon certain varieties of the garden pea as giving the best hope of 

 success. He also recognised that it would be necessary to examine 

 and keep under observation not only every plant, but also every seed 

 produced. This was a very important point, for it enabled him to 

 argue back from the progeny to the constitution of the germ-cells of 

 the parents. But more important still was his recognition of the 

 fact that if ever students of heredity were to find their way among 

 the confused mass of details which their own experiments and 

 observations had brought to light, they must give up trying to 

 compare the offspring as a whole with its parents and confine 

 themselves to what may be called unit-characters. 



It is impossible to deal fully with Mendel's experiments ; but it 

 may be stated that so far as peas were concerned he limited himself 



* The word "hybrid" is used by Mendel for a cross between two races or 

 varieties as well as for a cross between two species. The same signification of 

 the word is adopted in this paper. 



