F. Pitt 113 



^1 X albino ferret cross (No. 21), which was polecat coloured, and there- 

 fore presumably heterozygous in constitution, three dark and one white 

 young resulted (Nos. 47 to 50)\ When two second-cross ferrets, 

 Nos. 19 and 21 (i.e. the produce of the F^ generation x albino ferrets), 

 were bred together they had five dark young ones to one white. A mating 

 of interest was that which has already been referred to between Nos. 20 

 and 21. The former was an erythristic female, the latter a dark male, 

 the produce of a hybrid x a white ferret. The alliance between Nos. 20 

 and 21 gave rise to two dark, one red, and three white ferrets. As re- 

 gards cranial characters, all skulls that I have been able to examine of 

 these hybrid x ferret crosses have been indistinguishable in every par- 

 ticular from those of pure-bred ferrets. Full details and measurements 

 of these skulls will be found in the table on p. 100. 



{h) Fi Generation x the Polecat. In 1916 I was fortunate in obtaining 

 another fine male polecat from Cardiganshire. He was mated with 

 No. 37, an ^i female by my first polecat. Her litter only numbered two. 

 These two youngsters appeared true polecats in every respect, having 

 the broad faces, dark coats, drab under-fur, and highly nervous disposi- 

 tions of the wild animal. I subsequently found that in cranial characters 

 too they were polecats, for their skulls were typical of 31. putorius. The 

 male died young, but the female lived to be eighteen months old, when 

 she too unfortunately succumbed to pneumonia without having bred. 

 This susceptibility to pneumonia is a characteristic of the wild animal, 

 most captive polecats sooner or later dying of it. Pure-bred ferrets 

 appear to be much more resistant to the disease. In temperament and 

 disposition this young female was quite the wild animal, she was 

 intensely nervous, bit whenever she got the opportunity, and in her 

 excitement was always ready to emit the horrible polecat smell ; in short 

 there was no trace of the ferret about her. 



(i) Weakening of Pigmentation in Hybrid x Ferret Crosses. Before 

 glancing back over the evidence that has been presented concerning 

 polecat X ferret hybrids, it may be as well to draw attention to the 

 weakening of pigmentation that occurs when the polecat-ferret hybrids 

 are bred back to the ferret, the three-fourths ferret offspring being much 

 paler than the first cross. These individuals are very like the ordinary 

 " fitchet " ferret, but still further dilution takes place when another back 

 cross is made. After this the pigmented individuals are very " washy " 



1 For information concerning this litter I am indebted to Mr Owen of Oswestry into 

 whose possession the parents had passed. 



