PRESENT CRISIS IN EVOLUTIONARY THOUGHT 7 



the environment no less than the organism. This is both a 

 true and suggestive thought; but does it not leave the natural- 

 ist floundering amid the same old quicksands? The historical 

 problem with which he has to deal must be grappled at closer 

 quarters. He is everywhere confronted with specific devices 

 in the organism that must have arisen long after the condi- 

 tions of environment to which they are adjusted. Animals 

 that live in water are provided with gills. Were this all, we 

 could probably muddle along with the notion that gills are 

 no more than lucky accidents. But we encounter a sticking 

 point in the fact that gills are so often accompanied by a va- 

 riety of ingenious devices, such as reservoirs, tubes, valves, 

 pumps, strainers, scrubbing brushes, and the like, that are 

 obviously tributary to the main function of breathing. Given 

 water, asks the naturalist, how has all this come into existence 

 and been perfected? The question is an inevitable product 

 of our common sense." (Smithson. Inst. Rpt. for 1915, p. 405.) 



Impressed with the difficulty of accounting for the phenom- 

 ena of organic adaptation by means of the far too general 

 and unspecific influence of the environment,, the orthogenetic 

 school of transformism inaugurated by Nageli, Eimer, and K61- 

 liker repudiated this explanation, and sought to explain or- 

 ganic evolution on the sole basis of internal factors, such as 

 "directive principles," or germinal determinants. According to 

 this conception, the elephant first developed his trunk under 

 the drive of some internal agency, and afterwards sought out 

 an environment in which the newly-developed trunk would be 

 useful. In other words, orthogenesis makes the organ precede 

 the function, and is therefore the exact reverse of Lamarckism. 



Evolutionists in general, as we have said, regard our present 

 plants and animals as the modified progeny of earlier forms, 

 understanding by "modified" that which is the product of a 

 trans-specific, as distinguished from a varietal or intra-specific, 

 change. To substantiate the claim that changes of specific 

 magnitude have actually taken place, they appeal to two prin- 

 cipal kinds of evidence, namely: (a) empirical evidence based 



