A REJOINDER 153 



been evolved a race of goats the individuals of which are 

 quite indifferent to the presence in their tissues of the 

 germs of Malta fever. In both cases the susceptible 

 individuals have been eliminated and the immune 

 have survived. What would Miss Wodehouse have ? 

 The reverse condition ! A race of weak and con- 

 tinually ailing cattle and goats, and no vigorous 

 ones. Truly then the metaphysicians would have 

 problems to solve, beside which those of to-day 

 would be easy and commonplace. 



But still we will accept for the moment her con- 

 ception of Nature as a place where the tsetse fly 

 should not prevail, and that, although it is a quite 

 natural thing, it is not an admirable one. Let us 

 then banish the tsetse fly. Has it ever occurred 

 to her that the severest struggle for existence 

 in Nature is not between widely separated orders 

 or genera, but between closely allied species ? If we 

 banish this fly, are we quite sure that somewhere 

 within the range of its geographical area there does 

 not lurk such another species, whose numbers at 

 present are by direct or indirect means kept down 

 by the operations of this " fitter " tsetse fly ? 

 Upon the destruction of the tsetse fly this partially 

 suppressed species would become dominant and 

 might conceivably introduce another trypanosome, 

 against which the present race of cattle have not 

 been evolved. Once more, therefore, through the 

 processes of elimination of those which have by 

 artificial interference been rendered unfit must 

 a new race be reared, and the rash disturbance of 



