Bui. 1090, U. S. Dept. of Agriculture. 



PLATE VI, 



Four Generations of Family 35. 



The young pair at the right is descended from 19 generations of matings of brother with sister. 

 Their parents, grandparents, and great-grandparents were all found to be alive and are shown 

 in the picture. There is little if any genetic variation left in this stock. The variation in pat- 

 tern, which persists, seems to be due to nontransmissible irregularities in development. 



