850 LIFE : OUTLINES OF GENERAL BIOLOGY 



possessing plants that the existence and evolution of the whole 

 animal kingdom has since depended. 



Prof. Minchin's suggestion as to the origin of green plants was 

 that they diverged from a stock of Flagellate Infusorians which 

 formed or became possessed of chlorophyll corpuscles or chromato- 

 phores. There are some of the Flagellate Infusorians that have a 

 mouth and digestive vacuoles and an animal way of eating, and yet 

 have chlorophyll corpuscles so that they can also live like plants. 

 In technical language they are said to combine the holozoic and a 

 holophytic mode of nutrition. An abandonment of predatory life, 

 a reliance on the photos3mthesis of organic substances, a consequent 

 accumulation of reserves, and a nemesis of sluggishness might 

 eventuate in a definite plant at a unicellular level. "It would be 

 interesting", Minchin said, "to know exactly what these chromato- 

 phores, at their first appearance, represent; whether they are true 

 cell-organs, or whether, as some authorities have suggested, they 

 originated as symbiotic intruding organisms, primitively indepen- 

 dent." It must be understood that a few Protozoa, such as Vorticella 

 viridis, have chlorophyll of their own, while others, like Stentor 

 polymorphus, have green symbiotic Algse. The establishment of a 

 partnership with symbiotic green Algae, e.g. Zoochlorella, occurred 

 repeatedly, e.g. in many unrelated Protozoa, in Hydra viridis, in 

 many Anemones and Alcyonarians, and in the simple planarian 

 worm, Convoluta (see section on Symbiosis). 



It is possible, however, that the green pigmentation of some 

 Flagellate Protozoa is not to be regarded as indicating a probable 

 origin for green plants. Minchin's view would postpone the evolution 

 of green plants till there were animals as definite as Flagellata, 

 whereas one inclines to think of the dichotomy as occurring at a 

 much lower level. As to Bacteria, Minchin regarded them as very 

 primitive, non-cellular, vegetative organisms, directly derived from 

 the primeval Biococci, and not, as some maintain, either degenerate 

 or highly-specialised cells. 



On Mereschkowsky's daring hypothesis already referred to, the 

 first type of protoplasm, my ooplasm, was represented by very minute, 

 very hardy, Biococci with the power of building up proteins and 

 carbohydrates from inorganic materials. From these arose Bacteria, 

 which were for a long time the only living creatures besides the 

 Biococci. Afterwards there evolved the Blue-Green Algae (Cyano- 

 phyceae) and the Fungi. These three groups — Bacteria, Cyanophyceae, 

 and Fungi — ^formed a Kingdom by themselves, a Kingdom without 

 symbiosis, the Mycoidea. 



When Mereschkowsky's second kind of protoplasm, amceboplasm, 

 appeared on the stage in a cooler sea, it was represented by minute 

 amoeboid Monera. These entered into partnership with Biococci, 

 and the Animal Kingdom began. In a typical animal cell the 



