I30 



FACTS AND FANCIES 



forms, which apply to the cephalopods and 

 trilobites as well as to the brachiopods, and 

 some of which, as the writer has elsewhere 

 shown, apply very generally to fossil animals 

 and plants. One of these is that different con- 

 temporaneous species, living under the same 

 conditions, exhibit very different degrees of 

 vitality and variability. Another is the sud- 

 den appearance at certain horizons of a great 

 number of species, each manifesting its com- 

 plete specific characters. With very rare ex- 

 ceptions, also, varietal forms are contempo- 

 raneous with the normal form of their specific 

 type, and occur in the same localities. Only 

 in a very few cases do they survive it. This 

 and the previous results, as well as the fact that 

 parallel changes go on in groups having no 

 direct reaction on each other, prove that vari- 

 ation is not a progressive influence, and that 

 specific distinctions are not dependent on it, 

 but on the " sovereign action of one and the 

 same creative cause," as Barrande expresses 

 ' it. These conclusions, it may be observed, are 

 not arrived at by that " slap-dash " method of 

 mere assertion so often followed on the other 

 side of tliese questions, but by the most severe 

 and painstaking induction, and with careful 



