PEDIGREE INHERITANCE. 
410 
or no importance. Starting with the fact that all properties' of living things 
vary, two far more natural groups of the variations can be made. To the 
first of these groups belong such properties as are advantageous or disad¬ 
vantageous to their possessors, the variation of which properties depends 
directly on the different changes of the conditions of life (soil, training, 
food, temperature, etc.), to which they conform by degrees through the 
serie*, of generations, or change again or disappear; these «acquired» pro¬ 
gressive or regressive variations, which are nothing else but the «adap¬ 
tations», are inherited under permanent conditions of life, and can be set 
down duly as the effects of the natural selection. Upon these variations 
artificial selection is ineffective unless the conditions are accordingly and 
systematically regulated, or, if not, its effect will be checked by the natit- 
ral selection, i. e., the adaptation, which causes, in most of the. cases, rever¬ 
sion. 1 The second group includes those properties which are neither ad¬ 
vantageous nor disadvantageous to their possessors, the variation of which 
indifferent properties does not depend on the conditions of life. These 
extraordinarily variable properties do not supply natural selection in the 
strict sense with matter, and their inheritance can be caused only by iso¬ 
lation or generally by those chances which pair such individuals as vary 
in the same direction in comparison to the average ; like breeds like ; the 
contrary, the disappearing of the indifferent variations, in incomparably 
more numerous cases, is also caused by the chances of possibilities, in this 
way that such specimens as vary in different directions pair. Artificial 
selection, on the other hand, is able to regulate the inheritance of the in¬ 
different properties perfectly. 
Advantageous or disadvantageous, progressive or regressive «adap¬ 
tive» properties on the one hand, and properties which are «indifferent» 
under given conditions, on the other, supply us with perfectly convenient 
terms to decide the nature and heredity of the variations. If by natural 
selection we mean the conditions of life, then we can extend the idea of 
natural selection over the totality of those accidents, chances of possibili¬ 
ties which accumulate in Nature, which cause matings between individuals 
1 I thank Prof. Dr. G. Entz sen., whose conceptions of natural problems are always 
characterized by an unprejudiced logic, for the following striking co mparison, which he 
kindly gave me on an occasion when speaking about this theme. The Professor compared 
the methods of the breeder with those of the physician. According to this analogy the phy¬ 
sician does not cure, but Nature cures : the intervention of the physician is confined to the 
intentional regulation of those circumstances which keep the progress of healing within 
the proper limits. So also the breeder’s power is restricted to the systematic regulation of 
those conditions, under whose influence the changes, which are attributed to the effect of 
the'artificial selection, are brought about. 
