DARWINISM'S PRESENT STANDING. 3 8 3 



carrying over? Has natural selection's claimed capacity to 

 effect species change, unseen by observer, untested by exper- 

 imenter, anv better or even other proof of actuality than 

 that just offered on behalf of species modification as a direct 

 result of the stimulus of varying environment and func- 

 tional exercise? I cannot see that it has. 



And this kind of argument, based half on observed facts 



and half on deduction, may be extended even farther on 



behalf of the theory that species change is the 



The same kind 

 of proof for non- direct reaction to environmental conditions. 



adaptive change. -p or t ] iere are manv ontogenetic variations pro- 

 duced directly in response to environment that are not 

 plainly adaptive ; many, indeed, between which and the 

 environmental conditions that produce them no reasonable 

 relation is apparent ; no relation, that is, that would be ex- 

 actly expected or could be foretold until empirically deter- 

 mined. In other words, many apparently non-significant 

 ontogenetic differences or variations appear as direct result 

 of environmental influence or stimulus. For example, indi- 

 viduals of certain species of the Crustacean phyllopod genus 

 Artemia show marked structural differences when grown 

 in salt water of varying density. These differences are in 

 the size and shape of the plate-like lateral gills, the seg- 

 mentation of the post-abdomen, the length of the caudal 

 flaps (telson) and the hairiness of these flaps. The size of 

 the whole body is also affected, individuals developing in 

 water of higher density being markedly smaller than those 

 which have been grown in less dense water. Now of all 

 these differences only two seem to have what I call a rea- 

 sonable relation to the environmental differences. The in- 

 creased proportional size of the gills shown by the Artemias 

 grown in denser water appears to be a regulatory change 

 connected with the smaller amount of oxygen in the \vater r 

 and the decreased size of the body may similarly be con- 

 ceived by some to be an expected concomitant of the 



