Unilateral Transmission 
four generations. Thereare other instances of what 
is sometimes awkwardly called the unilateral trans- 
mission of abnormal qualities. Edward Lambert, 
born in 1717, is said to have been covered with 
‘spines. His children showed the same 
peculiarity, which began to be manifest from 
the sixth to the ninth month after birth. One 
of his children grew up and handed on the 
peculiarity to another generation. Indeed, it is 
said to have persisted for five generations, and 
in the males only—unilateral transmission.” 
In our view, these abnormalities are of such a 
kind that they are only possible in connection 
with the male organ; in other words, they are 
mutations of the first of the four kinds cited 
above—those which appear only in connection 
with the male organ. 
It is a curious fact that the general rule in 
nature seems to be that the male is ahead of the 
female in the course of evolution. The sexes 
may be alike at a given period in the life-history 
of the species. Presently a mutation appears 
which is confined to the male alone; thus arises 
the phenomenon of sexual dimorphism. The 
next step in the evolution of the species is 
frequently a mutation on the part of the female 
which brings her once again into line with the 
male, and so the sexual dimorphism disappears, 
for a time at any rate. A good example of this 
is furnished by the sparrows; in the common 
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