PHYSIOLOGY OF PROTISTA. 69 



ical, electrical, and chemical irritation of their contractile 

 protoplasm. Consciousness and the capability of will and 

 thought are probably wanting in all Protista. However, the 

 same qualities are in the same degree also wanting in many 

 of the lower animals, whereas many of the higher animals 

 in these respects are scarcely inferior to the lower races of 

 human beings. In the Protista, as in all other organisms, the 

 activities of the soul are traceable to molecular motions in 

 the protoplasm. 



The most important physiological characteristic of the 

 kingdom Protista lies in the exclusively non-sexual "pro- 

 pagation of all the organisms belonging to it. The higher 

 animals and plants multiply almost exclusively in a sexual 

 manner. The lower animals and plants multiply also, in 

 many cases, in a non-sexual manner, by division, the form- 

 ation of buds, the formation of germs, etc; But sexual 

 propagation almost always exists by the side of it, and often 

 regularly alternates with it in succeeding generations (Meta- 

 genesis, vol. i. p. 206). All Protista, on the other hand, pro- 

 pagate themselves exclusively in a non-sexual manner, and 

 in fact, the distinction of the two sexes among them has 

 not been effected — there are neither male nor female Protista. 



The Protista in regard to their vital phenomena stand 

 midway between animals and plants, that is to say, between 

 their lowest forms ; and the same must be said in regard to 

 the chemical composition of their bodies. One of the most 

 important distinctions between the chemical composition of 

 animal and vegetable bodies consists in the characteristic 

 forrhation of the skeleton. The skeleton, or the solid scaffold- 

 ing of the body in most genuine plants, consists of a sub- 

 stance called cellulose, devoid of nitz'Ogen, but secreted by the 



