24 THE THEORY OF EVOLUTION 



of life, worm-tubes, trilobites, brachypods, and snails 

 (among them a genus which still exists Pleurotomaria 

 of two species), these representing already fairly de- 

 veloped organisms. Other finds in Brittany are dubious. 

 But obvious limbs of starfish (Crinoidse) occur. 



The pre-Cambrian fauna appears therefore to be about 

 as perfect as that of the Cambrian formation itself. 



Conclusions from (1) : 



(a) The first organisms appear together, not succes- 

 sively, in types or groups clearly separated from each other. 



Most of the invertebrate classes are found. 



Many forms, it is true, carry the impress of simplicity 

 (' clumsiness ' it might be termed), like the Crabs ; the 

 Snails are still small and but slightly typical ; the Cepha- 

 lopods are only represented by puny forms with a flattish 

 shell x (in contrast to the manifold crooked and orna- 

 mented shells of the later representatives of this group). 



(6) Only one group (Trilobites) shows already a 

 very profuse branching into divergent differ entiated 

 forms. Fifty genera and about 150 species. 



(c) Monocellular organisms are preserved Fora- 

 minifera but they by no means form the chief 

 component of the primary fauna (as the terrestrial 

 evolutionary hypotheses demand) ; ( from the beginning 

 of animal life we are already infinitely far removed ' 2 

 i.e. the ' beginning ' of life had not been thus imagined. 



1 Kayser : Lehrbuch der Geolog. Formationskunde, p. 80. 



2 E. Koken: Die Vorweltundihre EntwicJdungsgeschichte, Leipzig, 1893, 

 p. 82. This remark of Koken' s is to be understood from the standpoint of 

 certain hypotheses of evolution which prescribe a fauna of entirely different 

 character. 



