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THE AMEBIC AN NATURALIST [VOL.LV 



Lamarckism at the present time, among American 

 biologists, has all but disappeared. Some palaeontolo- 

 gists, who in reading the records of the past find that 

 whenever new conditions for existence occurred, new 

 forms of life admirably adapted to those conditions ap- 

 peared, are prone to believe that the environment has in 

 some way directly molded these new inhabitants to its 

 bounds. Since this performance has occurred again and 

 again, they are a bit skeptical of the selectionist tenant 

 that each occasion has had to await, not only the acci- 

 dental occurrence of a favorable germinal variation, but 

 of a host of them, which must in turn be sifted and par- 

 celed and perfected by natural selection into that adapt- 

 edness to the surroundings which characterized the or- 

 ganisms in question. Various students of geographical 

 distribution also are inclined to regard the direct action 

 of environment as instrumental in molding the fauna of 

 a given region. In brief, those who look at the problems 

 of evolution from wide perspective tend to postulate that 

 altered function or environment, if long continued, in 

 some way modifies descendants, but they don't tell us 

 how.' Those who view the problem from the standpoint 

 of the few generations intensively studied by the geneti- 

 cist, or from the germ-cell lineages of the embryologist, 

 or the chromosomes of the cytologist, almost without ex- 

 ception reject the Lamarckian interpretation. And it 

 can not be denied that the latter have an incomparable ad- 

 vantage in directly testing the matter, since they have 

 their material in hand for direct observation or experi- 

 mental control. So it has come about that the believer 

 in Lamarckism, silenced if not convinced by the formid- 

 able array of negative evidence amassed against him, 

 and still more perhaps by his own inability, from the 

 basis of carefully controlled experiments, to cite specific 

 examples of inherited somatic acquirements, has sub- 

 sided into mute acquiescence or but faint-hearted advo- 

 cacy of his theory. 



The fertilized egg develops into an adult individual 



