280 THE PRINCIPLES OF Part 11. 



its own male and female sex to the hybrid offspring of 

 either sex. The same fact is likewise manifest, when 

 characters proper to the male are occasionally deve- 

 loped in the female when she grows old or becomes 

 diseased ; and so conversely with the male. Again, 

 characters occasionally appear, as if transferred from 

 the male to the female, as when, in certain breeds of the 

 fowl, spurs regularly appear in the young and healthy 

 females ; but in truth they are simply developed in the 

 female ; for in every breed each detail in the structure 

 of the spur is transmitted through the female to her 

 male offspring. In all cases of reversion, characters 

 are transmitted through two, three, or many generations, 

 and are then under certain unknown favourable con- 

 ditions developed. This important distinction between 

 transmission and development will be easiest kept in 

 mind by the aid of the hypothesis of pangenesis, whether 

 or not it be accepted as true. According to this hypo- 

 thesis, every unit or cell of the body throws off gemmules 

 or undeveloped atoms, which are transmitted to the 

 offspring of both sexes, and are multiplied by self- 

 division. They may remain undeveloped during the 

 early years of life or during successive generations ; 

 their development into units or cells, like those from 

 wdiich they were derived, depending on their affinity 

 for, and union with, other units or cells previously 

 developed in the due order of growth. 



Inheritance at Corresponding Periods of Life. — This 

 tendency is well established. If a new character appears 

 in an animal whilst young, whether it endures through- 

 out life or lasts only for a time, it will reappear, as a 

 general rule, at the same age and in the same manner 

 in the offspring. If, on the other hand, a new character 

 appears at maturity, or even during old age, it tends 



