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NOTES ON THE INABILITY OF NATURAL SELECTION 

 TO EXPLAIN CERTAIN STEPS IN THE EVOLUTION 

 OF PROTOZOA. 



By R. D. Greenaway. 



Ddring the past sixteen years biological study has made very 

 great strides in all directions. Especially is this true in the 

 departments of Heredity and Biogeny. The work of Mendel and 

 De Vries and the teachings of Bergson have revolutionised these 

 branches of biology. Constructive work has gone hand in hand 

 with rigorous criticism of previous theories. Many of the most 

 cherished conceptions of biologists have gone into the Medea's 

 Cauldron of criticism, and not a few have shared the fate of 

 Pelias. 



The doctrine of natural selection has not escaped its share 

 of criticism. The conviction, deepening every year, that evolu- 

 tion has occurred, has been attended by a growth of scepticism 

 as to whether the theory which up to the end of the nineteenth 

 century was held to have solved the riddle of organic existence 

 really does so. This scepticism is no new thing ; witness the 

 objection, still with us (though robbed of much of its force by 

 recent discovery), that incipient stages in the development of 

 really useful structures would be too insignificant to secure 

 survival. But of late three more fundamental difficulties have 

 presented themselves. Firstly, the uselessness of many specific 

 characters ; secondly, the discovery of the fact that germinal 

 variations (the only hereditary ones), are not the same as the 

 minute fluctuations in every direction which were formerly 

 believed to be of hereditary value. Finally, it is argued that, 

 since true germinal variation is definite and comparatively 

 infrequent, the development of highly complex organs (like 

 the vertebrate eye) through the selection of random variations 

 (difficult enough to conceive even if given a multiplicity of such 

 variations in every direction) now becomes unthinkable. 



