THE FIXITY OF SPECIES. 69 
In a recent book, “Creation or Evolution? A Philo- 
sophical Inquiry,’ George Ticknor Curtis says: “The 
whole doctrine of the development of distinct species out 
of other species makes demands upon our credulity which 
are irreconcilable with the principles of belief by which 
we regulate, or ought to regulate, our acceptance of any 
new matter of belief.” 
