4 PALAEONTOLOGY. 



The present survey of the evidences of organic beings in 

 the earth's crust commences with the lowest or most simple 

 forms, and will treat chiefly of the remains of the animal 

 kingdom. 



A reference to the subjoined "Table of Strata" (fig. 1) will 

 indicate the relative position and age of the geological forma- 

 tions cited, in connection with their characteristic fossils. 



Organisms, or living things, are those which possess such 

 an internal cellular or cellulo-vascular structure as can receive 

 fluid matter from without, alter its nature, and add it to the 

 alterative structure. Such fluid matter is called " nutritive," 

 and the actions which make it so are called "assimilation" 

 and " intus-susception." These actions are classed as " vital," 

 because, as long as they are continued, the " organism " is said 

 "to live." 



When the organism can also move, when it receives the 

 nutritive matter by a mouth, retains oxygen and exhales 

 carbonic acid in respiration, and has for the principal tissues 

 quaternary compounds of carbon, hydrogen, oxygen and 

 nitrogen, it is called an "animal." When the organism is 

 rooted, has neither mouth nor stomach, retains carbon in 

 respiration and exhales oxygen, and has for the chief tissues 

 binary or ternary compounds, it is called a "plant." But 

 the two realms of Nature called "plants" and "animals" are 

 specialized members of the one greater group of living things ; 

 and there are numerous organisms, mostly of minute size and 

 retaining the form of nucleated cells, which manifest the 

 common organic characters, without the superadditions of 

 truly distinctive plants or animals. Such organisms are 

 called " Acrita,"* and include the Amorphozoa or sponges, the 

 Rhizojjoda, or foraminifers, the Polyci/stinem, the Diatomacece, 



* Gr. «, expressing want or absence; krino, to separate ; signifying a want 

 of distinction or differentiation of tissues and organs. The group has since 

 been called "Protozoa," Gci\ protos, first; zoe, life or living thing. 



