Reviews — Prof. A. Oaudnj — On Evolution. 



37 



other progresses : we shall see in the Secondary epoch the 

 reign of reptiles ; in the Tertiary epoch the reign of birds and 

 mammals ; in the Quaternary epoch the reign of man. Thus taken 

 in its entirety the history of the world shows progressive develop- 

 ment. The evolutions proper to the Primary periods whilst 

 admitting that, taken as a whole, the history of the world has pre- 

 sented the spectacle of progress, we must bear in mind that all 

 classes have not developed in a continuous manner during geological 

 times. 



" We have seen that the Pteropoda, Cephalopoda, Ostracoda, 

 Brachiopoda, Merostomata, and Insects, have attained in the Primary 

 epoch a high degree of perfection, and a greater size than at the 

 present period. 



" One of the most curious results of palseontological study has been 

 to show that each one of the epochs of the world has had its own 

 special development. There have been forms which have been 

 specially designed for it ; with it has begun their reign, with it 

 their reign came to an end. This will be seen on glancing at the 

 subjoined table, wherein I have indicated the path which the develop- 

 ment of one part of the primary animals has followed. I have 

 represented each group by a branch which I have drawn more or 

 less thickly clothed with leaves according as the development has 

 been greater or less. 



Quaternary 

 Tertiart 



Secondary 

 Pfrmian and 



CARBONIFiiRuUS 



Devonian 



Silurian 



Cambrian 



"We see in this table how ephemeral have been the Graptolites. I 

 have already noticed that these forms, born in the Cambrian, do not 

 extend beyond the Silurian rocks. 



" Some of the Hydroid Coelenterates of more recent epochs may 

 have arisen from them, but then they have ceased to be Graptolites ; 



