IN THE TROPICS. 
353 
their germinal representatives, segregate in the germ cells of 
a cross-bred plant in such a manner that all possible combi¬ 
nations of the characters occur in equal numbers in the germ 
cells—the combination of the two characters of one pair in 
the same germ cell being impossible. 
Mendel also showed in 1870, in the case of crosses between 
different forms of Hieracium, that the behaviour of certain 
characters cannot be described in the same simple fashion. 
In the case of peas the particular characters which Mendel 
selected for observation showed the phenomenon of domi¬ 
nance. That is to say, one of each pair of parental characters 
was so preponderant that it was difficult or quite impossible 
to detect the other in the hybrid. In the case of other 
characters, however, Mendel observed intermediate forms in 
his hybrid peas. The hybrid Hieraciums were also more or 
less intermediate in appearance between their parents. 
Since 1900 Mendel’s Law of segregation has been shown to 
apply to a large number of characters in a variety of plants 
belonging to widely separated natural orders. In the case of 
a large number of such characters dominance has been found 
to occur, whilst in a further considerable number the hybrid 
forms (heterozygotes) show a more or less intermediate 
character. The same pair of characters (apparently )has, more¬ 
over, been found to show in some cases dominance in others 
blending. 
In other cases again a number of further complications 
may be introduced. 
A considerable group of these may be summed up under 
the head of latency of characters. Thus, when a character 
not visible in either of the parents makes its appearance in 
the offspring, we must suppose that this character, or the 
capacity for producing it, was present in a latent condition in 
one or both of the parents (Tschermak). 
In the case of so-called “ reversion on crossing’* of which 
examples have been given, a latent character seems to be 
rendered visible by the act of crossing and appears in the 
