944 MINNESOTA BOTANICAL STUDIES. 



(b. ) Complete Individualism. — The best known and per- 

 haps the most typical form of complete individualism 

 is represented by the higher lichens. Most authors are 

 agreed that the fungal symbiont has entirely lost the 

 power of independent existence, while the alga may exist 

 independently. Some recent experiments would, however, 

 lead me to believe that the algae likewise have lost the "power 

 of continued independent existence. Lichens would therefore 

 form complete individualism. The association of the algae 

 with Hydra viridis perhaps belongs to this category. The pha- 

 gocytes are as yet not sufficiently understood. They, in all 

 probability, establish a complete individualism in association 

 with the animal body, although no experiments have as yet 

 been made to substantiate this. Nor are the phagocytes gen- 

 erally considered as "organisms." 



Future experiments may demonstrate that the cell, and hence 

 the individual, is neither more nor less than complete individ- 

 ualism. The plasmic bodies, as chlorophyll granules, leuco- 

 plastids, chromoplastids, chromosomes, centrosomes, nucleoli, 

 etc., are perhaps simply the symbionts comparable to those in 

 the less highly specialized symbioses. Reinke expresses the 

 opinion that it is not wholly unreasonable to suppose that some 

 skilled scientist of the future may succeed in cultivating chlor- 

 ophyll-bodies in artificial media. 



IV. Compound Symbiosis. 



This is the occurrence of two different symbioses upon the 

 same host and is by no means uncommon. It is usually the 

 association of mutualism with parasitism. That is two or more 

 organisms form a mutualistic symbiosis and enter into an an- 

 tagonistic symbiosis with a third organism. Hueppe mentions 

 an instance in which two different species of bacteria unite be- 

 fore they can locate as parasites upon their common host. In 

 Manostomum bijugum, a parasitic worm found in birds, it is 

 known that two individuals always occur together. The in- 

 stance of sex- symbiosis, already mentioned, perhaps also be- 

 longs here. Compound antagonistic symbiosis, which is quite 

 common, is not included here. 



In conclusion, it may be stated that this communication sim- 

 ply represents an attempt to systematize the phenomena of 

 symbiosis, thus forming an aid to their future study. 



