148 EVOLUTION AND DISEASE. 
many suppose, especially when each suspected case is 
submitted to rigid analysis. I shall, however, first of 
all consider atavism in relation to secondary sexual 
characters, and then proceed to the study of super- 
numerary digits and limbs, and supernumerary mamme 
and nipples. It will be to the reader's advantage 
before perusing those sections to study carefully 
the remarks made on dichotomy, for of all examples 
mistaken for atavism, dichotomy claims by far the 
greatest number. 
Atavism in relation to Secondary Sexual characters.— 
As Darwin points out, two distinct elements are in- 
cluded under the term “inheritance ”—the transmission 
and the development of characters. The distinction is 
so important, especially in its bearing on the question 
of atavism, that the two conditions will be illustrated 
by concrete examples. 
In most species of the deer tribe it is the rule for the 
male alone to possess antlers, yet it is a well attested 
circumstance that under certain diseased conditions of 
the sexual organs, especially atrophy or degeneration 
of the ovaries, rudimentary horns which are never shed 
appear in the female. 
This shows us that the female is in possession 
of secondary sexual organs in virtue of transmission, 
yet they remain latent as a rule, and only become 
developed under extraordinary circumstances. The 
same holds good for those cases of hens who for years 
lay eggs, yet eventually cease to do so, put on one side 
the plumage proper to their sex, and adopt more or less 
completely that of the cock. 
