458 Proceedings of the Boycd Physical Society. 



tive character, affect tlie vegetative system ; others, such as 

 heat and markedly varied nutrition — more of the nature of 

 real stimuli — operate on the reproductive energies. Some 

 influences, such as light, are more important in regard to 

 the sensory and nervous systems of animals, while others of 

 a grosser nature affect more conspicuously other parts of the 

 organism. Or again, modifying the central column of my 

 diagram, the progress of research should make it possible to 

 draw up a series of tables in which the influence of external 

 factors (such as heat) might be illustrated in operation on 

 the protoplasm, on the cells, on the tissues, on the organ, on 

 the organism as a whole, and even on the species. In regard 

 to general adaptation, such an analysis has been sketched by 

 Mtinsterberg, but in spite of fundamental researches like those 

 of Frommann, the relative scantiness of available material 

 makes such a task as yet premature. It hardly needs to be 

 stated that except in the case of mechanical factors, like 

 currents, the influence affects the protoplasm first, and thence 

 saturates throughout the system. The organism cannot be 

 supposed to react directly to external influence, as litmus 

 paper to an acid. 



7. Physiological Rationale of Environmental Influence. — In 

 many cases it is easy to understand why a given external 

 change should be followed by a definite organismal variation. 

 That an increase of food should augment size, that hypertrophy 

 should be followed by sluggishness, that drought should in- 

 duce ency station, that heightened temperature should stimulate 

 activity, that starving and cold should produce reduction of 

 size, and so on, are intelligible enough results; but many cases 

 of apparent influence remain which are by no means so 

 readily explained. In a general way the influences must 

 be referable to one of two classes, — to those which tend to 

 increase constructive processes, passivity, storage of energy ; 

 or to those which tend to increase destructive processes, 

 activity, and expenditure of energy. They may in fact be 

 classified as anabolic and katabolic influences respectively 

 (see table). But it would still be difficult to classify, unless 

 altogether outside these, the more formal action of the 

 environment in determining shape, mode of growth, and 



