170 BIOLOGY FOR BEGINNERS 



Functions of any circulatory system. 



Transfer of food from digestive organs to tissues. 

 Transfer of oxygen from lungs to tissues. 

 Transfer of waste from tissues to excretive organs. 

 Excretory organs. 



Pair in each segment, well developed. 

 Nervous system. 



Simple " brain " and ventral nerve chain. 



Separate nerve branches, much higher than previous animals studied. 



Locomotion: 



Adaptations for, 



1. Body muscles, two layers, different motions. 



2. Setae with their own muscles. 



3. Habit of flattening the " tail " region in burrow. 



Burrowing: 



Adaptations for, 



1. As above. 



2. Habit of swallowing earth through which it goes. 



3. Evidence shown in "castings." 



Food-getting : 



Food, celery, lettuce, meat, etc., from surface, ta^en below; organic 



matter in soil, 

 (manner of eating; use of pharynx and air pressure). 



Economic value: 



Earthworm, loosens and enriches soil, brings up fresh earth, 

 takes down organic matter, 10 tons per acre per year. 



Reasons for development of circulatory system in higher forms. 

 More numerous cells. 

 Greater division of labor. 



All tissues not in reach of food or air by mere osmosis. 

 Need for transportation system. 



Analogous organs: 

 Definition. 



Examples: setae, cilia, pseudopodia, all for locomotion, 

 similar examples from fish, bird, man, etc. 



Parasitism. 



Results: 



Harm or death to host. 



Degeneration. 



Loss of organs. . 



Absolute dependence. 

 Need for vast reproduction. 



to parasite. 



