Heredity 197 



"This diagram shows the nine types called for by 

 Mendel's theory. Of these, EL, BC, SL, and SC are 

 no longer hybrids at least they have no latent char- 

 acters, and will therefore reproduce true to seed. Of the 

 remaining five types, BI and SI are hybrid only with 

 reference to length of head, and SbL and SbC only with 

 reference to beards; while Sbl is hybrid with reference 

 to both characters, as in the preceding generation. 



"It will readily be seen that the types BL and BC can 

 be separated from the others even by external appearances, 

 and obtained in a pure state. BL is the type shown at 

 the left in the second row in the picture, and all its prog- 

 eny was like it, showing that it conformed to theory. BC 

 is the type shown at No. 3 in the second row of heads ; 

 being pure, it should reproduce itself true to type, which 

 it did, with an easily explained exception to be noted be- 

 low. The type BI (shown at No. 2, row 2), being hybrid 

 with reference to length of head, should produce again 

 all types based on this character, and it did this, as is seen 

 in heads Z-4, row 3. Referring again to the above 

 diagram, it will be seen that the types SL and SbL cannot 

 be distinguished by external characters. SL will of course 

 reproduce true to type, while SbL will reproduce SL } 

 SbL, and BL. Now SL and SbL being mixed together in 

 the selection made in the second generation, we shall find 

 a large percentage of SL mixed with some SbL from which 

 it cannot be distinguished, and a small percentage of BL 

 in the third generation. Heads 6 and 7, row 3, show that 

 the types called for actually occurred. Types SI and Sbl 

 of the diagram appear alike externally, and were there- 

 fore selected together in the second generation (see head 



