vip LINKAGE 
spring recorded is small. In such cases the data are 
usually fitted to the nearest ‘““Mendelian”’ ratio even 
Fic. 28.—Photograph of the P; (1 and 2) and F, (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, 
