56 



THE CHAIN OF LIFE. 



Upper Cambrian ; and they continue under very similar forms 

 all through the Palaeozoic, and are represented by the millepore 



.^'h,.- 



l^Avk^ 



Fig. 39rt. — Fenestella LyelU {Da.vison). A Carb:.niferous Bryozoan. 



corals of the present day. Fig. 40 represents a form found at 

 the base of the Siluro-Cambrian, and Fig. 41 shows forms 



characteristic of the Carboniferous Lime- 

 stone. 



If we turn now to the sea-mosses (Bryozoa), 

 we have a group of minute polyp-like animals 

 inhabiting cells not unlike those of the Hy 

 droids, and which form plant-like aggregates. 

 But the animals themselves are so different 

 in structure that they are considered to be 

 nearer allies of the bivalve shell-fishes than 

 of the Corals. They are, in short, so different, 

 that the most ardent evolutionist would 

 scarcely hold a community of origin between 

 them and such creatures as the Graptolites and 

 Millepores, though an ordinary observer might readily confound 

 the one with the other. These animals appear at the beginning 

 of the Siluro-Cambrian, and such forms as that represented in 

 Fig. 39, very closely allied to some now living, are large consti- 

 tuents of some of the limestones of that period. Other forms, 



Fig. 40. — Chaetetes 

 fibrosa. A tabulate 

 coral with micro- 

 scopic cells. Ljwer 

 bilurian. 



