48 THE SURVIVAL OP THE UNLIKE. [l. 



the gardener says that his begonias and geraniums and 

 callas must have a "rest," or they will not thrive. But 

 in time he can so far break this habit in most plants as 

 to force them into activity for the entire year. These 

 budding days of April, therefore, are the songs of re- 

 lease from the bondage of winter which has come on as 

 the earth has grown aged and cold. 



I must bring still one more illustration of the survi- 

 val of the unlike, out of the abundance of examples 

 which might be cited. It is the fact that, as a rule, new 

 types are variable and old types are inflexible. The stu- 

 dent of fossil plants will recall the fact that the lirio- 

 dendrons, ginkgos, sequoias, sassafrasses and other types 

 came into existence with many species, and are now go- 

 ing out of existence with one or two species. Williams 

 has considered this feature, for extinct animal forms, at 

 some length in his new "Geological Biology." "Many 

 species," he writes, "which by their abundance and 

 good preservation in fossil state give us sufficient evi- 

 dence in the case, exhibit greater plasticity in their char- 

 acters at the early stage than in later stages of their 

 history. A minute tracing of lines of succession of 

 species shows greater plasticity at the beginning of the 

 series than later, and this is expressed, in the systematic 

 description and tabulation of the facts, by an increase 

 in the number of the species." "When species are 

 studied historically, the law appears evident that the 

 characters of specific value * * * present a greater 

 degree of range of variability at an early stage in the 

 life -period of the genus than in the later stages of that 

 period," So marked is this incoming of new types in 

 many cases that some students have supposed that actual 

 special creation of species has occurred at these epochs. 



