5i6 TRANSMISSION 



the single character in question; for example, hybrids of Jerseys 

 and Shorthorns would not breed pure individuals^ either breed, 

 though pure Jersey and pure Shorthorn characters would appear 

 freely. 



If we are to consider many characters at once, we may easily 

 satisfy ourselves as to the chances of an absolutely pure indi- 

 vidual arising out of a hybrid ancestry. 



If one fourth of the population arising from a hybrid ancestry 

 can be said to be pure as to a single character, the question 

 arises as to what proportion of this number can be considered 

 as "pure" with respect to two characters. 



From the fact that this second character enjoys the same 

 chances as to purity as did the first, we conclude that one fourth 

 of the number, or one sixteenth of the whole (| X J), will be 

 pure as to two characters. By the same reasoning we know that 

 \ X \ X \ carried to any number of terms will express the chance 

 of an individual being pure with respect to the corresponding 

 number of characters. If many characters are involved, there- 

 fore, the chances of a pure individual arising out of mixed 

 breeding are exceedingly slight, and our chance of being able to 

 " pick him out " by his appearance is still more remote. 



Experimental evidence. 1 It remains now to inquire somewhat 

 carefully into the evidence upon which these propositions are 

 founded. 



Mendel's first experiments were conducted with garden peas, 

 and covered the following characters : 2 



1 . Differences in form of ripe seeds, either round and 

 smooth or with shallow wrinkles, or else angular and deeply 

 wrinkled. 



2. Differences in the color of seed albumen (endosperm) 

 either pale yellow, bright yellow, orange, or green. 



3. Differences in the color of the seed coat, white, gray, 

 gray brown, leather brown with or without violet spotting. 



4. Differences in form of ripe pod, whether inflated or 

 constricted between seeds. 



1 For a translation of Mendel's original report, see Bateson, Mendel's Prin- 

 ciples of Heredity, pp. 40-103, from which are taken the data herein given. 



2 Ibid. pp. 45-46. 





