282 
THE PRINCIPLES OF 
Part II. 
have moulted two, three, or four times ; and these 
modifications of plumage are regularly transmitted. 
Inheritance at Corresponding Seasons of the Year . 
— With animals in a state of nature innumerable 
instances occur of characters periodically appearing at 
different seasons. We see this with the horns of the 
stag, and with the fur of arctic animals which becomes 
thick and white during the winter. Numerous birds 
acquire bright colours and other decorations during the 
breeding-season alone. I can throw but little light on 
this form of inheritance from facts observed under 
domestication. Pallas states , 21 that in Siberia domestic 
cattle and horses periodically become lighter-coloured 
during the winter ; and I have observed a similar 
marked change of colour in certain ponies in England. 
Although I do not know that this tendency to assume a 
differently coloured coat during different seasons of the 
year is transmitted, yet it probably is so, as all shades of 
colour are strongly inherited by the horse. Nor is this 
form of inheritance, as limited by season, more remark- 
able than inheritance as limited by age or sex. 
Inheritance as Limited by Sex. — The equal trans- 
mission of characters to both sexes is the commonest 
form of inheritance, at least with those animals which 
do not present strongly-marked sexual differences, and 
indeed with many of these. But characters are not 
rarely transferred exclusively to that sex, in which they 
first appeared. Ample evidence on this head has been 
advanced in my w 7 ork on Yariation under Domestica- 
21 4 Novas species Quadrupedum e Glirium ordure/ 1778, p. 7. On 
the transmission of colour by the horse, see 4 Yariation of Animals, &c. 
under Domestication,’ vol. i. p. 21. Also vol. ii. p. 71, for a general 
discussion on Inheritance as limited by Sex. 
