PHYLOGENY. 83 



standpoint. It is only in the most intelligent of the 

 Mammalia, and in man, that we behold social and in- 

 tellectual qualities which express something more than 

 a mere routine of material existence. 



Since Protozoa are very fragile, even when pos- 

 sessed of shells of mineral salts, we cannot expect to 

 discover the actual date of their first appearance on 

 the earth. Nevertheless they have been recently dis- 

 covered in the later Archaean (= = Huronian) beds of 

 France. Some of the simplest Crelenterata, however, 

 (the Actinozoa), have deposited lime salts in the septa 

 of their digestive chambers, and in some instances over 

 their entire surface, so that their preservation has been 

 assured. Thus we can prove that the simplest coral 

 animals appear in the oldest rocks of sedimentary ori- 

 gin, the Cambric. Probably Vermes, and positively 

 Echinodermata, Mollusca, and Arthropoda (Trilobita), 

 also appear in the Cambric. Vertebrata appear defi- 

 nitely in the Siluric ; their supposed appearance in the 

 Ordovicic being very doubtful. 



The paleontologic history conforms to the syste- 

 matic order in so far as it shows that the Ccelenterata 

 appeared first, and the Vertebrata last, in time. A 

 more complete correspondence between the two his- 

 tories is found in the divisions of these branches, and 

 I will take up the Vertebrata as the one of whose be- 

 ginning we know the most, and are likely to know 

 more. 



2. THE PHYLOGENY OF THE VERTEBRATA. 

 a. PJiylogeny of the Classes. 



As the illustrations of evolution in the present work 

 are mainly drawn from the Vertebrata, I go somewhat 

 into detail in discussing the phylogeny of that branch. 



