COPRINUS STERQUILINUS 165 



one hundred united simple monosporous mycelia ninety-nine have 

 given up the whole of their contents to one mycelium, thus enabling 

 it to produce a fruit-body which may develop and liberate spores. 



At first, perhaps, one might be disposed to consider that the 

 one mycelium of the one hundred united ones which has produced 

 a fruit-body in our hypothetical culture simply acts as a parasite 

 upon the other ninety-nine. In a sense this parasitism must be 

 admitted ; for the favoured mycelium absolutely exhausts its 

 fellows and carries out the business of developing a fruit-body 

 which produces and liberates spores at their expense, but with its 

 own cells and nuclei. But another explanation — that of social 

 organisation in the interests of the species — seems preferable to the 

 parasitic one. 



The social explanation of the facts illustrated in Fig. 91 may be 

 stated as follows. For the production of so large a structure as a 

 fruit-body of Coprinus sterquilinus a very considerable amount of 

 mycelial contents is required. To obtain this amount of mycelial 

 contents a single simple monosporous mycelium must become 

 master of a certain minimum mass of the nutrient substratum — 

 a small dung-ball or a mass of dung equivalent thereto. But for 

 a monosporous mycelium to obtain mastery of so much of the sub- 

 stratum under natural conditions must often be difficult or impossible 

 to accomplish owing to competition from other species of fungi ; 

 and perhaps, when there is only a single spore of C. sterquilinus in 

 a dung-ball, the mycelium which proceeds from it but rarely succeeds 

 in becoming massive enough to form a fruit-body. However, in 

 a single dung-ball, at the moment of its deposition, there must often be 

 a large number of spores of C. sterquilinus embedded.^ Let us suppose, 

 as already done in (2), that in one particular dung-ball one hundred 

 spores of C. sterquilinus are so embedded that they are equally dis- 

 tributed throughout the ball and that all of them germinate and give 



' A large fruit-body of Coprinus stcrqxiiJirms may produce as many as 100,000,000 

 spores (Vol. Ill, p. 223). In a pasture many fruit-bodies may come up on horse- 

 dung plats. The spores are carried by the wind on to the herbage, to the leaves 

 and stems of which they cling with great tenacity (Vol. Ill, p. 229). A horse when 

 grazing must often swallow thousands or even tens of thousands of them. They 

 pass down the alimentary canal unharmed, so that all of them are extruded in the 

 faeces. 



