FACTOKS OF INHERITANCE. 47 



published in 1866 were not appreciated at that time, and 

 lay neglected and forgotten until again brought to light 

 in 1900 by the botanists Correns, Tschennak, and De 

 Vries. The illuminating researches of Mendel have since 

 been confirmed and extended by a vast number of ob- 

 servers, among whom one may mention Bateson, Punnet, 

 and Doncaster, in this country. 



The laws of inheritance have been worked out by cross- 

 ing closely allied races of plants and animals differing 

 from each other by certain easily recognisable characters, 

 and observing the results in the subsequent generations. 

 For example, if two individuals of the snap-dragon 

 (Antirrhinum majus] are crossed, one belonging to a con- 

 stant race with crimson flowers and the other belonging 

 to a constant race with ivoryywhite flowers, the hybrid 

 offspring will all bear pink flowers like those of neither 

 of the parents. But if these hybrids are now inbred 

 (crossed among themselves), a second generation will be 

 obtained of mixed character. One quarter of this second 

 generation will bear crimson flowers like those of the 

 first parent, two quarters (half of the whole number) 

 will bear pink flowers like those of the first hybrid, 

 while the remaining quarter will produce white flowers 

 like those of the second parent. The crimson and the 

 white-flowered plants of this second generation will breed 

 true if crossed among themselves, like the original pa- 

 rental stocks ; but the pink-flowered plants will never 

 breed true. On the contrary they will always split, like 

 the original hybrid, into three kinds and in the same 

 proportions (In 2ri In). This example well illustrates 

 the fundamental principle of the segregation of the heredi- 

 tary factors in the gametes of the hybrid individual, 

 which is the foundation stone of Mendel's theory of 

 heredity. The facts are accounted for as follows : 

 Individuals belonging to each of the constant parent 

 stocks give rise to germ-cells or gametes of similar in- 

 heritance ; all the gametes of the first parent will con- 



