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LOCK : STUDIES IN PLANT BREEDING 
Darwin’s “ Origin of Species ” was published in 1859, his 
44 Variation in Animals and Plants in 1868.” 
Mendel’s paper on peas was read in 1865, and that on 
Hieracium in 1869. In 1865 also appeared Wichura’s account 
of willow hybrids (78), in which the strictly intermediate 
form of most of the hybrids examined was strongly em¬ 
phasized. 
In 1881 Focke in his 44 Die Pflanzen-Mischlinge ” gave an 
able account of the progress of the knowledge of hybrids up 
to that date. This work contains also a useful historical 
summary. Mendel’s work is briefly referred to, but its full 
importance is not recognized. 
Nægeli’s 44 Mechanisch - physiologische Theorie der 
Abstammungslehre ” was published in 1884, and Weismann’s 
well-known essays upon Heredity were appearing about the 
same time. 
In 1889 Galton in his 44 Natural Inheritance ” gave a very 
clear account of his application of statistics to the problems 
of heredity. From various human characters he deduced 
the value ^ for 44 filial regression.” Although most of his 
own observations were directed to the elucidation of the 
laws of 44 normal variability” Galton recognized the probable 
importance of discontinuous variations in evolution. 
Macfarlane in 1892 (48) showed that the minute structure 
of plant hybrids agrees with their external appearance in 
showing characters usually intermediate between those of 
the parental forms. 
Millardet’s remarkable account of 44 False hybrids ” ap¬ 
peared in 1894. In the same year Bateson’s work 44 Materials 
for the Study of Variation” was published. The author 
criticized a number of biological conceptions then current, 
and showed that the whole tendency of the material accumu¬ 
lated was to indicate the importance of discontinuous 
variations in the origin of species. Without attempting a 
rigid definition—hardly possible at that stage of the inquiry— 
Bateson indicated the difference between the two kinds of 
