SYMBIOLOGY — THE BIOLOGICAL RELATIONSHIPS OF ORGANISMS 1 53 



is less close and even less interdependent than it is among the several 

 living inclusions of the cell of higher plants and animals, and even less 

 closely interdependent than the associations of the somatic cells of the 

 higher multicellular organisms, but is an independent autonomous struc- 

 ture nevertheless. ' 



(a) Semi-individualism. — This is perhaps of wide occurrence. It is 

 represented by the lower Hchens in which the algal symbiont is capable of 

 leading an independent existence, while the fungus can not. In the lowest 

 crustaceous lichens there is perhaps mere mutualism, since several investi- 

 gators state that the symbionts may Hve independently as fungus and 

 alga. Some algae seem to form semi-individualism with animals. Ac- 

 cording to Kiihn, Pleurococcus brachypodis and Pleurococcus chlopodis occur 

 only upon the body (among the hair) of the two and three-toes sloths. 

 Simple-celled, chlorophyll-bearing algas or chlorophyll-bodies have been 

 found in representatives of the following genera of the animal kingdom; 

 Ameba, Dactylospora, Difflugia, Hyalosphaenia, Helepera, Arcella, 

 Cochhopodium, Actinosphaerium, Rhaphidiophrys, Acanthocystis, Het- 

 erophrys, Chopdropus, Spaerastrum, Ciliophrys, Vorticella, Epistylis, 

 Ophrydium, Vaginicola, Euplotes, Urostyla, Uroleptus, Stichotricha, 

 Spirostomum, Blepharisma, CHmacostomum, Stentor, Cyrtostomum, 

 Microthorax, Paramecium, Loxodes, Coleps,Lionotus, Amphileptus,Lacry- 

 maria, PhyaHna, Holophrya, Euchelyodon, Euchelys, Spongilla, Hydra, 

 Vortex, Mesostomum, Hypostomum, Derostomum, Couroluta, Anthea, 

 Bouellia, Idotea. In many instances the green particles occurring within 

 the animals are simply remnants of chlorophyll derived from the algae 

 upon which the animal feeds. In other instances there is an undoubted 

 sjonbiotic association of an alga and the animal. 



(ft) Complete Individualism. — The best known and perhaps the most 

 t3^ical 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, indicate that the algae likewise 

 have lost the power of continued independent existence. Lichens would 

 therefore form a complete individualism. The association of algs with 

 Hydra viridis and with forms of soil amebae and ciliata, perhaps 

 belongs to this category. 



The true significance of the Uchen symbiosis does not receive general 

 recognition. Botanists still persist in classifying them among the fungi. 

 Some place them in a separate and independent group, recognizing the 

 fact that they "are not as other plants" but steadfastly refuse to recognize 

 the true reason why they should be given an independent group position. 

 Most of the botanists see in the relationship between alga (the gonidia of the 



