PROTOZOA AND ENVIRONMENT 287 



tinuance of the race of the parasite. Some parasites 

 may alter greatly in appearance if they are forcibly 

 introduced into hosts other than their proper one. 

 In other cases no change occurs. Certain Protozoa 

 have been shown to inherit acquired characters, while 

 in others transference to a new host seems to awaken 

 the power to reproduce possible ancestral features, 

 that may have been in past ages, but have gradually 

 disappeared in the course of evolution. 



Among the Protozoa, by far the greater number 

 live and feed much as other animals do, but among 

 the free-living forms, found usually in fresh water, 

 there are a few that combine the modes of life of 

 both plant and animal. Up to the present, no 

 animal has been described, so far as is known, that 

 has the power possessed by the plant, of using simple 

 mineral constituents of the soil or of water alone as 

 food. But a few, such as the Euglena found in 

 pond-water, and the group of beautiful organisms, 

 claimed by some as plants and by some as animals, 

 known as the Algal flagellates, possess peculiar cor- 

 puscles, usually green, within their bodies. These 

 contain some pigment, either chlorophyll or some 

 substance having the same properties, and thus are 

 able to absorb carbon dioxide, decompose it under the 

 influence of sunlight, and utilize the carbon for build- 

 ing new protoplasm or for food materials. 



Other Protozoa are unable to use inorganic food 

 materials, nor do they prey upon living animals. 

 Such are the peculiar Mycetozoa. The bulk of their 

 nourishment is obtained from dead and decaying 

 materials, such as bark of trees, tan refuse, dejecta 



