174 TRANSMISSION OF ACQUIRED CHARACTERS 



of colour after particular diet, callosities induced on the skin by 

 pressure, e.g. those at first produced on the finger-tips of one who is 

 learning to play the violin, dwarfing of animals in confined space, 

 increased muscular development by exercise, atrophy of muscles 

 through disuse, chronic fatigue of nerve-cells, alterations in the walls 

 of the food-canal through particular diet, changes in the skeleton 

 as the result of specialised activities, increased growth of hair, etc., 

 after importation to a warm climate, accumulation of fat as the result 

 of modified nutrition, and so on through a long list. 



To understand the question clearly we must spend a little 

 time and thought over it. Let us briefly consider the various 

 relations between an organism and its surroundings. 



1. Relation of Dependence between Organism and Environ- 

 ment. It is a familiar fact that a living creature is de- 

 pendent upon its surroundings. A great part of life consists 

 in action and reaction between the organism and its environ- 

 ment. It is a profound commonplace that between the animate 

 system so incomprehensibly unified and its inanimate milieu, 

 there is a continual coming and going of matter and energy. 

 On this life depends. The may-fly during its short aerial life 

 must breathe even if it does not feed ; the philosopher requires 

 his dinner, just as his dog does. This may be called the relation 

 of constant and normal environmental dependence necessary 

 to the development and to the continuance of the organism. 



2. Transient Adjustments. But surroundings are changeful, 

 and the living creature changes with them. A great part of 

 life consists of effective responses to external changes ; consciously 

 or sub-consciously the organism adjusts itself to changes in its 

 environment, or works in the direction of adjustment. There 

 is bright sunshine and our pulse beats more quickly ; the external 

 temperature rises and we perspire. Thousands of these changes 

 are familiar, saving life from monotony. Yet in regard to 

 many there remains no abiding result that can be detected. 

 There are structural changes attendant on normal nerve-fatigue, 

 but in rest and food we gain almost complete recuperation. No 



