22 THE MENDEL JOURNAL 



Disregard of this has led to all sorts of misconceptions, 

 and even to actual misinterpretation of results. 



The second idea running through Mendel's experi- 

 ments was that of following the results of a 

 cross through several (at least three) generations. 

 This is an extremely important point, for, in 

 conjunction with the next idea of separate 

 records of all individuals, it permits clear evidence 

 to be obtained from the progeny, of the kind of 

 factors present in the germ-plasm of the parents, 

 whether those factors are visibly manifested in the 

 latter or not. The possibility of carrying out this 

 idea evidently depends upon the fertility of the 

 hybrids, and it is not the least of Mendel's incidental 

 contributions to the methodical study of heredity 

 that he so clearly saw the importance of experimenting 

 with forms which produce fertile hybrids. Most 

 investigators before his time, and for long afterwards, 

 were content to make crosses between different 

 species and races and to note the results in the 

 first generation, without attempting to carry the 

 experiment any further. But this only led to 

 confusion, for, as we now know, the hybrids may be 

 in appearance exactly like one parent or exactly 

 like the other, or partly like one and partly like the 

 other, or again like neither parent but with a character 

 of their own, while all the time perhaps the factors 

 determining the original characters of both parents 

 are being treated by the cell- divisions leading up to 

 the formation of the germ-cells of the hybrids as 

 perfectly distinct entities, ready to show themselves 



