and their Classification. 289 



ology. This division has boen introduced by H/eckel. 

 Previous to him all living beings were classified into the two 

 kingdoms, animal and vegetable. But a number of living 

 beings have been found to present each, in external form, in 

 internal structure and in all vital phenomena, so remarkable 

 a mixture or combination of distinguishing animal and vege- 

 table characteristics, that it is impossible, except arbitrarily, 

 to account them as belonging to either realm. Most of these 

 beings are so small that with the naked eye they can be seen 

 either with difficulty only, or not at all. The majority of 

 them have, consequently, become known only during the last 

 fifty years, since the more general use and improvements of 

 the microscope. And just as soon as they became known 

 they gave rise to endless and unprofitable disputes as to their 

 nature and position in the organic scale. Many of them 

 botanists called animals, and zoologists plants ; i. e., neither 

 wanted to own them. Others again were declared to be 

 plants by botanists, and animals by zoologists ; '^. e., both 

 parties claimed them. Keally they hold a position which 

 can only by violence be incorporated with either realm ; and 

 it was a happy idea of H.eckel to end the fruitless fight 

 over these doubtful beings by erecting the neutral ground 

 they occupy into a kingdom by itself, a' kingdom in a certain 

 way below, yet intermediate to, the two organic kingdoms 

 hitherto recognized. These beings are called neuters, be- 

 cause they are neither plants nor animals, or "protists," 

 l)ecause they are lowest in the organic scale, i. e., first after 

 inorganics or unliving beings. 



The division of the animal kingdom into Vertebrata and 

 Invertebrata, or Evertebrata, as they were afterward called, 

 Ave owe to Lamarck, who introduced this distinction toward 

 the end of the last century. 



" Vortebnita are divided into amniota and anamniota, accordinsly as the 

 dermal and cuticular elements of the ventral lamin* are in development 

 reflected upwards from the medio-ventral line, so as to meet along the 

 medio-dorsal line, and form thus the foetal envelope known as the amnion- 



