60 THE LAMARCKIAN DOCTRINE 



are special creations. (3) There may have been evolution, but 

 evolution miraculously directed. This belief implies that species 

 changed in adaptation to a changing environment, not because the 

 environment, acting on them, caused the change, but because a 

 Power, in a sense outside the environment, moulded them into 

 adaptation to it without using it as an instrument. It is, however, 

 a rule, as good in science as in the ordinary affairs of life, not to 

 appeal to the supernaturnal until natural explanations have been 

 exhausted. 



92. A variety of the belief in miracle has sometimes been 

 advocated by men of science chiefly botanists. God and miracle 

 are not mentioned, but we are told that species are fitted to their 

 environments by means of an inherent adaptive growth-force ; that 

 is, we are asked to believe that offspring not merely surviving 

 offspring, but offspring in general tend to vary from their parents 

 in such a way as to be better fitted to the environment, and that 

 thus evolution results. If we examine the evidence on which the 

 supporters of this, the ' bathmic,' hypothesis rely, we find no very 

 strenuous attempt to distinguish between variations and modifica- 

 tions between inherent alterations dependent on alterations in the 

 germ-plasm, and changes that result merely from a differential play 

 of stimuli. Many of the examples quoted by them appear to be 

 nothing other than what Mr A. Bacot has termed ' repertoire 

 patterns.' l Thus the plant Berberis vulgaris bears leaves in a 

 moist and spines in a dry atmosphere. Hippuris has two forms, 

 one terrestrial and the other aquatic, which may be converted, the 

 one into the other, by changing the environment, the leaves under 

 the water growing long and undulating, those in the air short and 

 erect. It has been assumed by the supporters of the bathmic 

 theory that all these differences are germinal that the individual 

 that develops in the one way in the one situation, differs innately to 

 the extent of his differences from the individual that develops in 

 the other way in the other situation. But, as a fact, we have no 

 reason to suppose that they are other than acquired. They furnish, 

 however, very interesting evidence that nature may fit a species 

 for existence in two separate environments, in each of which it is 

 capable of flourishing, but in one of which, under one set of stimuli, 

 it develops characters different from those which it develops in the 

 other environment under another set of stimuli. Presumably, such 

 species have evolved under conditions which rendered this capacity 

 for alternative development useful because the one environment 

 1 Nature, Jan. 3oth, 1908, p. 294. 



