330 Causes and Course of Organic Evolution 



genera are capable of chemical auto-nutrition by utilisation 

 of sulphur or iron compounds as sources of energy, by which 

 food material can be elaborated. Others show varying degrees 

 of pigment formation through a pink or bacterio-purpurin 

 phase to a yellow, a yellow-blue, a blue-emerald or emerald 

 stage, in which latter three absorbed sunlight becomes increas- 

 ingly utilized as a source of energy for formation of food com- 

 pounds. 



So it seems probable that the simpler blue-green and emer- 

 ald-green cyanophyceous algae, with their peripheral chro- 

 matophore, and frequently skene or -uTcath-arranged chromatin 

 threads, represent a slow evolution from more primitive color- 

 less types, in wliich chemico-energesis has been replaced by 

 Imnino-energesis. With increasing abundance of organisms 

 and their subsequent decay, some of the colorless autotrophic 

 bacteria assumed a saprophytic role, and still later througli 

 the stage of facultative parasitism many became purely para- 

 sitic, while others through a stage of facultative epibiotism 

 became largely or wholly epibiotic, and so originated animal 

 organisms. 



The pleomorpliism and enormous abundance of living fungi 

 is one of many parallel proofs that fresh-water and more espe- 

 cially land organisms always tend to vary more, and to give 

 rise to advancing and dominant lines, than do marine organ- 

 isms. So the 2670 genera with 24,000 species of existing fungi 

 far outnumber the entire assemblage of the algae. 



But the mode of origin of these has been variously accounted 

 for. We accept fully the view, propounded by De Bary, Sachs, 

 and many since, that the fungi are dechlorophyllized offshoots 

 from the algse, at different stages in the evolution of the latter. 

 For, witli advancing critical investigation of algoid and of 

 colorless or fungoid forms, the more perfectly do we recognize 

 the close continuity, structurally, that exists between both. 

 Thus of the Pleurococcacese, Protococcacese, Oocystaceae, and 

 Volvocacese, that we have regarded as groui)s connecting the 

 emerald Cyanophycese with the higher green algte (pp. 254, 

 308), pale green or colorless genera are now knoTNTi, like EomyceSy 



