158 THE GROWTH OF GROUPS 



early in January, nearly five months before their proper 

 time. Moreover, as though with a purpose, they spent 

 their winter sleep close to the surface instead of going 

 deep, a circumstance which would have been fatal to 

 them under nature, unless perhaps they had occurred in 

 a humid tropical climate. If such a race had appeared in 

 nature and found itself on an equal footing in other 

 respects, in the rate at which it was being thinned by foes, 

 and in the number of young produced by the females in 

 each generation, it follows that the parent species would 

 have been ousted from its food plant. Since the outward 

 appearance of the new race would be the same as that of 

 the old, an entomologist might wonder how it was that 

 L. decemlineata had thus changed its habit in the course 

 of a few years, being unconscious of the fact that L. 

 decemlineata was extinct and some variety of it occupying 

 its place. 



Let us leave the subject of parasitism and turn to 

 congenital disease. The word disease no longer ex- 

 presses a single idea. Formerly it meant any disordered 

 state in which a person might appear at birth or into 

 which he might fall during the course of his life, any state 

 of erroneous action of a system or part of the body 

 appearing suddenly or gradually, being terminable or 

 interminable during the period of life and lessening that 

 period or not as the case may be. From this medley of 

 states, which was the category of disease, were separated 

 certain obvious congenital deformities such as hare-lip, 

 club-foot, extra digits, etc. The distinction between 

 such congenital states and disease is usually regarded as 

 evident, although some pathologists have expressed the 



