72 



LINKAGE 



spring recorded is small. In such cases the data are 

 usually fitted to the nearest "Mendelian" ratio even 



3 



FIG. 28. Photograph of the Pi (1 and 2) and F I (3 and 4) birds in such 

 a cross as that of Fig. 26. 



though discrepancies are apparent. Even in species 

 where a number of different characters have been 

 studied these are often recorded in separate tables, 



