x] Sex-limited Inheritance 177 



properties like those elsewhere proved to attach to other 

 dominants. 



In the two cases next to be considered we meet an 

 important new feature in the fact that reciprocal crosses 

 between pure types give dissimilar results*. Though both 

 examples to be discussed are only imperfectly explored, the 

 facts elicited are so striking that some preliminary notice of 

 them is called for. We may confidently anticipate that 

 further search will discover other comparable instances. It 

 will be seen that these phenomena point very plainly in the 

 same direction as those previously described, to the con- 

 clusion, namely, that, in the types used, femaleness depends 

 on the presence of a definite dominant factor. 



The Cinnamon Canary. 



The first case of a sex-limited distinction between 

 reciprocal crosses is provided by the evidence as to the 

 descent of what is called "Cinnamon" in Canaries. The 

 characteristic of these canaries when adult is the presence 

 of the pale drab colour known as Cinnamon in the feathers, 



* Since this chapter was set up, Doncaster has discovered a most 

 important new fact regarding the grossulariata case which at once brings it 

 into line with that of the Cinnamon Canary about to be described. These 

 new results were reported to the Dublin Meeting of the British Association 

 (Sept. 1908). The experiments enumerated in the text were, it will be 

 observed, incomplete in so far as the mating wild gross. ? x lact. $ had not 

 been made. The results of this mating are now known. Families thus 

 bred consist of males grossulariata, and females lacticolor \ In other words, 

 the ordinary wild grossulariata in districts where lacticolor is unknown, are 

 in reality a race of which the males are pure grossulariata, though the 

 females are in reality hybrids of lacticolor, and so continue froYn generation 

 to generation. The normal female grossulariata and the F l $ grossulariata 

 bred from lact. $ x gross. $ are thus seen to be identical in composition. 

 Whether a gross. ? has a gross. $ for a mother, or a lact. $ for a mother 

 makes no difference to its composition and properties. This fact is one of 

 the most striking to which genetic research has yet led. It affords strong 

 confirmation of the interpretation of the series of phenomena given in the 

 text, and enables us to see in the evidence both as to the grossulariata case 

 and as to the other cases which follow a consistent mass of testimony all 

 pointing in the same direction. In a recent paper (114) Doncaster accepts 

 the view here suggested. It must of course still be remembered that 

 attractive though the present suggestion is, by reason of its simplicity, we 

 have no proof that the natural scheme may not be more complex. 



B. H. 12 



