254 METAMORPHOSIS 



Since it has been shown that here water itself has a formative influence on 

 the plant and induces adaptations directly, we are bound to conclude that in 

 other cases, as in aquatics which no longer have land forms, and in xerophytes 

 which do not alter their habit although in the presence of abundant water, 

 the direct effect of the medium does not exhibit itself in the life-cycle of the 

 individual, but has developed during the evolution of the species and has now 

 become permanent. We involuntarily reach the conclusion that species are 

 variable, but that many of their characteristics are hereditary adaptations. 



Although the formative effect of the external world has been abundantly 

 proved we must not suppose that the plant reacts to all factors with purposeful 

 adaptations. We need advance only one example of such a reaction due to 

 external influences which does not appear to be of any service to the plant, 

 namely, the palmella form in Basidiobolus. It is often by no means easy to 

 determine whether a change in shape is to be considered as an adaptation or 

 as ' a product of a fortuitive mechanism ' (BERTHOLD, 1898) ; for, in keeping 

 with the views they hold on certain general questions, some botanists are inclined 

 to look for adaptations everywhere and to find them, whilst others are content 

 to discover merely the operation of a purposeless mechanism. In the latter 

 case they follow in the footsteps of physicists and chemists, and recognize in 

 the organism the selfsame forces which operate in the inorganic world. If we 

 look on all these changes as ' adaptations ', we have still the all-important 

 problem to solve : why does the plant react in a purposeful way ? It reminds 

 one of an organism possessed of intelligence, and the problem appears to be 

 beyond our power to solve. 



We come now to a most important question, viz. whether results springing 

 from the operation of these forces in the organic world obey the same laws 

 which they do in the inorganic, or whether we have here to deal with quite 

 special relations. Before" attempting to discriminate between these two 

 alternatives let us glance at what we have learnt in this connexion from our 

 experimental treatment of the problem of plant formation. Wherever we look we 

 are forced to the conclusion that every change in an organism is a complex 

 process, which is due never to one solitary cause but to a large number of co- 

 operating factors. The phenomena are thus remarkably complicated, and when 

 we compare them with those of other sciences the probability of being able to 

 arrive at a mathematical-physical explanation of them is very slight. As every 

 one knows, Astronomy can calculate with the greatest exactness the path by 

 which a body in obedience to the law of gravity moves towards another ; if a 

 third body makes its appearance influencing the path of the first, the course 

 may still be determined empirically, though no longer strictly mathematically. 

 Glancing now at meteorological phenomena no one doubts that they obey simple 

 physical laws ; in principle, these are quite intelligible, but an explanation of 

 an individual case or an exact prediction of a meteorological condition is not 

 possible. If then in any science, only that may be considered as explained which 

 can be expressed in terms of mechanics, how may we dare to hope ever to arrive at 

 a physical explanation of life ? Still, as in the science of Meteorology, we may 

 succeed in reaching, at least, a knowledge of principles. In inanimate nature 

 alone there are plenty of phenomena which mock our attempts to refer them 

 to mechanical causes, e. g. the inherent characters of bodies. The peculiar 

 characteristics of an element are incomprehensible and inexplicable ; even more 

 inexplicable is the fact that compounds of these elements assume new charac- 

 ters not to be referred to combinations of those of the elements themselves. 

 It is impossible to affirm that the characteristics of living bodies are distinct in 

 principle from those of non-living ; all we can say is that we are equally de- 

 barred from a knowledge of those of either. Generally speaking, a mechanical 

 explanation of life is out of the question ; at most a physico-chemical 

 explanation is all we can hope for (ALBRECHT, 1901). 



