C. B. Bridges & Thomas Hunt Morgan 
Sex-Linked Inheritance in Drosophila [PDF ebook] 

Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. It has been found that when certain characters enter a cross together (i. E., from the same parent) their factors tend to pass into the same gamete of the hybrid, with the result that other ratios than the chance ratios described by Mendel are found in the F2 generation.