On the Hybridising of Duels. 237 



Skeat, asking him what term he would suggest. It was 

 finally decided to adopt Professor Skeat's proposal of the 

 root yevoç, prefixed by the Greek numerals, so that while all 

 crosses may be designated as hybrids, a cross between two 

 species becomes a digen, between three species a trigen, 

 between four a tetragen, between five a pentagen, and so on. 



I propose first of all to give a description of the different 

 crosses, and leave to the second portion of the paper any 

 deductions that are to be drawn. 



The Pintail-Mallard. 

 The only birds I have had of this cross are a pair bred in 

 Norfolk, which I received through the kindness of Mr. J. H. 

 Gurney. 



The Spotbill-Mallakd. 

 . Cross (1) M co S = M.S. 



Cross (2) (Mc,S)c,M =3 M.S. 



Cross (3) M ^ [(M ^ S) ^ M] = 11 M.S. 



Cross (4) (M e-, S) c, [(M ^ S) <-* M] * = 7M. 5S. 

 This cross has been performed in the four above-mentioned 

 ways, which, as will be noted, chiefly differ from each other 

 by the greater preponderance of the Mallard element. 2 



1 Immediately under the heading of each cross will be given the exact method 

 or methods by which that cross was obtained. The Drake is always placed first, 

 and each mating is contained within brackets. By this means it is possible to 

 give, in short, a rough pedigree of each bird. As for example : — [(M c ^ S) ^ 

 (P c-, M)] e-, |Z c^[(M c-, S) c, M] } . 



This may be written out genealogically, as follows, taking the different single 

 letters only, until it has all worked down. Each bracket represents a generation. 

 The numerals only refer to the letter they immediately precede. By this means 

 the different proportions of each species in any one bird may be seen at a 

 glance. 



M =-3 S 



I 

 M c-3 S P c-o M M.S =-3 M 



I I I 



ILS. «t> P.M. Z ^o 3 M.S. 



I I 



2 M.S.P. t-, 4 Z. 3 M.S. 



I 

 4 Z. 7. M. 3 S. 2 P. 



The sign c-, is one used in genealogies, and appears to the writer, after due 

 consideration, to be more correct than the usual x or multiplication sign. 



2 It may here be noticed that, as a rule, individuals of the same cross and 

 generation are remarkably uniform. Two forms may sometimes be recognisable, 

 but, in these cases individual variation is very slight, so that there will never be 

 any doubt as to which type any particular individual should be referred. 



