PRE-CAM BRIAN LIFE 59 



out of a richer fauna, or that in the beginning of 

 things the gaps and missing links between different 

 forms of Hfe were even more pronounced than at 

 present. This, however, would be likely to occur 

 if the plan of creation was to represent at first 

 different types, with few forms in each ; to produce, 

 in short, a sort of type collection representing the 

 whole range of organization by a few characteristic 

 things rather than to give a complete series, with 

 all the intermediate connections. Such a mode of 

 introduction of life is not a priori improbable, how- 

 ever at variance with some prevalent hypotheses. 



Beginning with the higher Invertebrates, we must 

 not conclude that we have altogether lost the Trilo- 

 bites. The fragments referred to this group may 

 represent at least a few species, and it would be 

 very interesting to know more of these as to their 

 relations to their successors, and whether they are 

 tending to lower or more embryonic forms. The^^^ 

 bivalve Crustaceans (Ostracods) may be regarded as 

 inferior in rank to the Trilobites, but are still very 

 complex, and specialized animals and a specimen 

 silicified in such a manner as to show the interior 

 organs testified that, as far back as the Carboniferous 

 at least, these creatures were as highly organized as 



