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, ete. 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 chenuical composition of their bodies. One of the most 
important distinctions between the chemical composition of 
animal and vegetable bodies consists in the characteristic 
formation 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 nitrogen, but secreted by the 
