134 SUMMARY 



2. Tliore is no definite indication, so far, that animals 

 found in these or simihir habitats can live indefinitely 

 without oxygen, though it is a possibility. 



3. Worms living in the tidal zone are probably not de- 

 pendent primarily on anaerobic metabolism for their sur- 

 vival during low tide. 



4. A partial transition to anaerobiosis may be of great 

 importance for the survival of earthworms in rain-soaked 

 soil. 



5. A high resistance of non-parasitic worms to the ex- 

 perimental deprivation of oxygen is observed, in general, 

 in those organisms which are found normally in envir- 

 onments lacking oxygen. 



6. The resistance to oxygen deficiency varies with en- 

 vironmental factors (temperature) and internal factors 

 ( hydration, nutrition ) . 



7. Most intestinal and tissue helminths show a consid- 

 erable resistance to the experimental deprivation of 

 oxygen. 



8. The eggs of helminths are quite resistant to the lack 

 of oxygen but they require aerobic conditions for their 

 development. 



9. The controversy over aerobiosis versus anaerobio- 

 sis of intestinal worms is based on a misunderstanding, 

 since the type of metabolism of various helminths may be 

 different in identical environments depending on the or- 

 ganization of the animals. The same is true of tissue 

 helminths. 



Echinoderms. 



1. Adult echinoderms seem not to occur in anaerobic 

 surroundings and they are quite sensitive to complete 

 lack of oxygen. 



2. Eggs and sperm of echinoderms exhibit a greater 

 resistance to experimental anaerobic conditions than do 

 adults. 



