THE WONDERS OF LIFE 



protists many of the bacteria, especially, belong to this 

 class, and also many fungilla (pJiycomycetes); among 

 the metaphyta the fungi (mycetes), and among the 

 metazoa the sponges. I have already spoken of the 

 many peculiarities of metabolism in the ubiquitous 

 bacteria; while many of them cause putrefaction, they 

 at the same time feed on the parts of other organisms 

 which have died. The fungi feed for the most part on 

 the decayed remains of plants and the products of putre- 

 faction which accumulate on the ground. In this 

 character of scavengers they play the same important 

 part on land as the sponges do at the bottom of the sea. 

 But a number of small groups of the higher plants and 

 animals have, as a secondary habit, turned to sapro- 

 sitism. Among the metaphyta we have especially the 

 monotropea (to which our native asparagus, nionotropa 

 hypopitys, belongs) and many orchids (neottia, coral- 

 lorhiza). As they find their plasm directly in the 

 decayed matter in the woods, they have lost their 

 chlorophyll and green leaves. Among the metazoa 

 many of the vermalia, and some of the higher animals, 

 such as the rain-worm and many tube-dwelling annelids 

 (the mud-eaters, limicolcE), etc., live on putrid matter. 

 The organs which their nearest relatives use for obtain- 

 ing, breaking up, and digesting food (eyes, jaws, teeth, 

 digestive glands) have been entirely or mostly lost by 

 these saprosites. Many of them form a transitional type 

 to the parasites. 



By parasites, in the narrower sense, we understand, 

 in modern biology, only those organisms which live on 

 others and derive their nourishment from them. They 

 are numerous in all the chief divisions of the plant and 

 animal kingdoms, and their modifications are of great 

 interest in connection with evolution. No other circum- 

 stance has so profound an influence on the organism as 

 adaptation to a parasitic existence. Moreover, there is 



234 



