THE FUNGI : ASCOMYCETES AND BASIUIO.MYCETES 341 



Fungi, cannot be compared with the sexuality in the Algae, and there are 

 many other differences which might be detailed. 



Whence then, we may ask, came the Fungi ? One modern view, which 

 is steadily receiving more support from mycologists, is that they are a 

 completely independent group, standing midway between the plants and 

 animals and having no direct connection with either, except that at the dawn 

 of evolution all life is believed to have had a common origin. In fact it has 

 been suggested that the Fungi, or their ancestors, may have originated before 

 either the plants or the animals. It is pointed out that in the absence of any 

 form of life it would be possible for organic substances to have existed on 

 the surface of the earth without undergoing decomposition, that is to say, 

 organic substances derived from purely chemical reactions. On such food 

 the first organisms could have lived as saprophytes. 



From these saprophytic organisms, which may be regarded as the first 

 Fungi, plants would be produced as a result of the evolution of a photo- 

 catalvtic pigment which enabled them to synthesize their own food rather than 

 rely upon material already elaborated. Parasitism then followed as the 

 primitive saprophytic Fungi transferred their attention to plant life as a 

 second means of obtaining food. In this connection we may note that even 

 at the present time nearly all parasitic Fungi, however specialized, can fall 

 back on a saprophytic existence if need be, as can be seen by their ability to 

 grow on artificial media. 



According to this view the animal kingdom was the last to be evolved, 

 and again came from these saprophytic organisms, but here, instead of either 

 making its own carbohydrates or living on the carbohydrates made by the 

 plants, the animals devoured the plants and Fungi completely and thus a 

 holozoic mode of nutrition became established.* It is interesting to note 

 in this connection that there is at the present day a group of Fungi known 

 as the Zoopagaceae, which have adopted the habit of preying upon protozoal 

 animals and Nematodes, which suggests that the hypothesis here outlined 

 is not entirely fanciful. 



If, then, the Fungi are really older in an evolutionary sense than either 

 plants or animals, and if both kingdoms have originated from them, we should 

 expect to find features exhibited which were characteristic both of animals 

 and plants. This we certainly do. The simplest green plants are the Algae, 

 the simplest animals the Protozoa. We have already indicated some of the 

 points of similarity between Algae and Fungi ; analogous though not as 

 clear comparisons are found with the Protozoa. We can clearly connect 

 the Plasmodium of the ^lyxomycetales with the Protozoa through the 

 Rhizopoda ; in fact some zoologists consider that the ^Nlyxomycetales are 

 animals and include them in the Protozoa as an order, the ]\Iycetozoa. 

 On the biochemical side the formation of glycogen, which is a distinctly 

 animal substance, as a metabolic product in place of starch, is another strong 

 link with the animal kingdom. On the other hand, true cellulose is formed 



* An alternative theory of the evolution of living organisms is referred to under Chemo- 

 synthetic Bacteria on p. 359. 



