or PLANTS AND ANIMALS. 173 



plants of extreme simplicity of organization. The more 

 ancient the geological formation the greater is the diflFer- 

 ence between its fossil plants and those now living ; whilst 

 on the other hand, the Tertiary deposits which are, com- 

 paratively speaking, recent in the history of creation, con- 

 tain in addition to species now extinct, botapieal remains 

 which are identical with species now living. There has 

 therefore been a gradual approximation of vegetation to its 

 present condition. 



There appears to have been a similar progression in the 

 animal creation. All naturalists admit that the animal re- 

 mains found in the Primary or Paleozoic rocks are charac- 

 terized by great simplicity of organization, and that the 

 animals of this period present the least resemblance to those 

 now living. The articulata are mostly trilobites — animals 

 which evidently belong to the lower order of the Crus- 

 taceans. There is an incompleteness and want of develop- 

 ment in the form of their body, that strongly reminds us 

 of the embryo among the crabs. The class of insects is 

 entirely wanting. The radiata are represented by the Crino- 

 idea, or lily-like zoophytes, animals remarkable for the sim- 

 plicity of their organization, and the peculiarly complicated 

 structure of their skeleton. The body of these Crinoids 

 was supported on a long and flexible column, -which was 

 attached to a rook or some other hard substance, at the 

 bottom of the sea. This column was composed of an im- 

 mense number of joints, through which an aperture de- 

 scended from the stomach to the base or support. The 

 bodies of the Crinoidea, like that of the Hydra, were sim- 

 ple digestive cavities surrounded with jointed tentaculae of 

 the same structure as the stem, which the animal had the 

 power of spreading abroad for the purpose of grasping its 

 prey. These animals belonged to, the class of Echinoderms, 

 15* 



