114 Polecat, Ferret, and Polecat-Ferret Hybrids 



in appearance and exactly like the average dark ferret. Whether there 

 is a true dilution factor involved appears doubtful, the lighter appear- 

 ance of the animal being due to a smaller quantity of dark hairs in its 

 coat, not to reduction of the pigment in the hair, as in "dilute" mice, 

 rats, and rabbits. Were true dilute ferrets to occur I should expect them 

 to be a pearl-grey colour. In "fitchet" ferrets the lighter colouring, lighter 

 that is by comparison with polecats and their hybrids, is due to the 

 white or pale cream under- fur, to the cream basal portion of the longer 

 hairs, and to the general increase of cream coloured fur. 



V. Recapitulation and Conclusion. 



Attention has been drawn in this paper to the interesting material 

 for genetic study that is to be found in the polecat and ferret, the two 

 forms have been described, together with their points of difference and 

 resemblance, and it has been shown that the characters in which they 

 differ are such diversified ones as coat colour, cranial peculiarities, and 

 temperament. The doubt as to whether the ferret is a descendant of the 

 European or Asiatic polecats has been alluded to, and evidence has been 

 given that it at any rate will cross freely with M. putorius, the hybrids 

 being fertile inter se, and with either parent. The F^ generation shows 

 complete, or very nearly complete, dominance of the polecat type as 

 regards outward appearance, but what evidence is to hand indicates that 

 in cranial characters the ferret is dominant. When the hybrids were 

 bred back to the ferret the polecat coloration and temperament were 

 soon lost. Likewise when the hybrids were bred back to the polecat, 

 animals that were apparently pure polecats resulted. An interesting 

 result of the back crosses with ferrets (albinos) was the gradual weakening 

 of the colour in the pigmented offspring, due not to dilution of the pig- 

 ment in the hairs, but to a reduction in the amount of dark fur. Atten- 

 tion has also been drawn in this article to the erythristic varieties of 

 the polecat and ferret, and particulars have been given of the occurrence 

 of " red " polecats in the Aberystwyth district, together with some 

 evidence that this mutation has appeared comparatively recently, and is 

 inherited according to Mendel's law. In the case of the ferret it is shown 

 that erythrism is certainly dependant on a Mendelian factor, being 

 dominant to albinism and recessive to the black-brown coloration. 

 Both in the ferret and polecat erythrism seems to be correlated with 

 increased size, and certainly in the ferret is usually accompanied by a 

 quick temper and general increase of vitality. To the writer the most 



