192 DISCOVERY OH. 



flashed upon him all the possible effects of the struggle 

 for existence. In two days the entire draft of the paper 

 showing the application of the views to organic species 

 in general was sketched and posted to Darwin, who had 

 been working upon the verification of the same idea 

 for twenty years. Darwin had actually written out a 

 sketch of his theory in 1842 ; and in 1844 this sketch 

 was enlarged to 230 folio pages, giving a complete 

 presentation of the arguments afterwards set forth in 

 the Origin of Species. 



When Darwin received Wallace's paper he brought 

 the communication before Sir Charles Lyell and Sir 

 Joseph Hooker, and urged that it should be printed at 

 once. Upon their advice, however, he consented to let 

 an extract from the sketch of 1844 be presented to the 

 Linnean Society with Wallace's paper on July 1st, 1858. 

 " The one great result which I claim for my paper of 

 1858," said Wallace, " is that it compelled Darwin to 

 write and publish his Origin of Species without further 

 delay." 



For evolution to proceed in any particular direction, 

 it is necessary for variations in that direction to be 

 encouraged continually, and for the trend of tendency of 

 the parent to be inherited by the offspring. Variation 

 and heredity are thus complementary to each other ; and 

 until the laws by which they are determined are under- 

 stood, no evolutionary theory can be said to be complete. 

 The rule of the road of heredity was discovered in 1866 by 

 Gregor Johann Mendel, an Augustinian monk, Abbot of 

 the old monastery at Briinn, Austria ; but the biological 

 world remained unaware of it for thirty years, and 

 Darwin died without knowing of the epoch-making work 

 of his contemporary. " Had Mendel's work," says 

 Prof. W. Bateson, the leading authority upon it, " come 



