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 ’’ + (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,t 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 
* Linnean Society's Journal: Zodlogy, xi., 1872. 
¢ Linnean Societys Journal: Zodlogy, xx., 1887, pp. 189-274, 
496-505 ; also Mature, July 18, 1872. 
{ Zvolution without Natural Selection ; or, The Segregation of Spe- 
cles without the aid of the Darwinian Hypothesis, London (1885), 
pp. 1-8o. 
