LIFE ON THE EARTH. 213 



quires absolutely the admission of separate stemmata, 

 certainly for every principal group, apparently and 

 probably so for every genus or natural assemblage 

 of much resembling forms with similar structures. 



The explanation offered by most palaeontologists 

 is that these several stemmata are of independent 

 origin, separate creations in fact, using this term 

 to indicate a process unknown to us, by which the 

 Creator has provided for the appearance of new 

 forms and structures at definite times, and in certain 

 places, which it is in the province of palaeontology 

 to search out. The explanation offered in the hy- 

 pothesis of Mr Darwin, is that the groups of life 

 which appear to be and really are distinct, in the 

 Cambro-Silurian rocks, are not aboriginal forms ; but 

 derived from progenitors of far earlier date, belong- 

 ing to few types or to one; the original form, and 

 the transition forms being unknown to us. 



Now they are not unknown to us by any im- 

 possibility of being preserved, for the strata of the 

 Cambro-Silurian series are of a kind in which organic 

 remains of great delicacy are often preserved, and 

 indeed such are preserved in these very strata; and 

 by the hypothesis the life-structures which are lost 

 must have only gradually differed in their nature 

 from those which are preserved. It follows, there- 

 fore, that the earlier living progenitors of the Cam- 



