210 SYMBIOSIS 



however, has so far seen fit to protest against the incongruity of 

 attempting to base evolution upon such pathology as here entailed. 

 Even Dr. Larger, as we have seen, was taken in by the " adapta- 

 tion " view of Parasitism. This is what Darwin says (p. 6) : 



There is, for instance, a fly (Cecidomyia) which deposits its eggs within 

 the stamens of a Scrophularia, and secretes a poison which produces a 

 gall, on which the larva feeds ; but there is another insect (Misocampus) 

 which deposits its eggs within the body of the larva within the gall, and 

 is thus nourished by its living prey ; so that here a hymenopterous insect 

 depends on a dipterous insect, and this depends on its power of producing 

 a monstrous growth in a particular organ of a particular plant. So it is, 

 in a more or less plainly marked manner, in thousands and tens of thou- 

 sands of cases, with the lowest as well as with the highest productions of 

 nature. 



And so it may well be, I should say, in a million cases 

 without, for that matter, the phenomenon constituting aught 

 but a pathological sequence one that cannot possibly lead to 

 progressive evolution. We must at last learn to distinguish 

 the two paths in Biology : the symbiotic and the non- or anti- 

 symbiotic, if the present muddle is to be avoided. The fly 

 Cecidomyia, so we must argue, has abused its one time symbiotic 

 power in order to gain certain expedient ends by means of short 

 cuts. Its very power of producing the gall is but a travesty of 

 its former symbiotic power, with its manifold and correlated 

 capacities of stimulating the physiological economy of the plant. 

 The fly now is merely poisonous to its food-plant and causes 

 monstrosity, whereas it used to be helpful to the plant and furthered 

 its welfare by counter-services. Powers of goodwill on either 

 side, painfully established during long ages of correlated useful 

 evolution, are 'now in course of being abused. In a symbiotic 

 relation, as we have abundantly seen, both organisms thrive, 

 and there is moreover a margin of benefit to the world of life. 

 But in the above instance both organisms are injured : the plant 

 by the wound, and the predaceous dipterous insect by becoming 

 the soil of infection consequent upon its transgressions against 

 the bio-social order of Nature. Darwin was astonished to find 

 that a hymenopterous insect may be superior in the art of 

 depredation to a dipterous one. But we may surely put the 

 case down to a corruptio optimi pessima. If, as Darwin has else- 

 where shown, those bees which indolently cut holes in the corolla 

 instead of obtaining the nectar normally, become debauched, 



