NEOLAMARCKISM 



405 



This was succeeded by Rev. J. T. Gulick's pro- 

 found essays " On Diversity of Evolution under 

 One Set of External Conditions"* (1872), and on 

 " Divergent Evolution through Cumulative Segre- 

 gation " f (1887). 



These and later papers are based on his studies on 

 the land shells of the Hawaiian Islands. The cause 

 of their extreme diversity of local species is, he 

 claims, not due to climatic conditions, food, ene- 

 mies, or to natural selection, but to the action of 

 what he calls the " law of segregation." 



Fifteen years later Mr. Romanes published his the- 

 ory of physiological selection, which covered much 

 the same ground. 



A very strong little book by an ornithologist of 

 wide experience, Charles Dixon,:]: and refreshing to 

 read, since it is packed with facts, is Lamarckian 

 throughout. The chief factor in the formation of 

 local species is, he thinks, isolation ; the others are 

 climatic influences (especially the glacial period), use 

 and disuse, and sexual selection as well as chemical 

 agency. Dixon insists on the " vast importance of 

 isolation in the modification of many forms of life, 

 without the assistance of natural selection." Again 

 he says: " Natural selection, as has often been 

 remarked, can only preserve a beneficial variation — it 

 cannot originate it, it is not a cause of variation ; on 



* Linnaan Society' s Journal : Zoblogy, xi., 1872. 



\ Linncean Society 5 Journal : Zoblogy, xx., 1887, pp. 189-274, 

 496-505 ; also Nature, July 18, 1872. 



X Evolution without Natural Selection ; or. The Segregation of Spe- 

 cies without the aid of the Darwinian Hypothesis, London (1885), 

 pp. 1-80. 



