280 
THE PRINCIPLES OF 
PiYRT II 
its own male and female sex to tlie hybrid offspring of 
both sexes. 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 
which 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 
