2 24 EVOLUTION, GENETICS, AND EUGENICS 



valley." It must be noted, however, that Drummond did not prove 

 his case with sufficient precision, and there is, as Escherich points out 

 in his beautiful study of termites, this difHculty, that, while the cast- 

 ings of earthworms are soft and loose, the earth-tubes and construc- 

 tions of termites are stony. 



Escherich does, however, admit that the termites have some 

 agricultural importance, and he points out that there are other serv- 

 ices to be put to the credit side of their account. They prune oflf 

 wood that has begun to go; they destroy rotting things, including the 

 bodies of small animals; they make for cleanliness and health. In 

 some low-lying tracts, as Silvestri has shown, there are dry stretches, 

 "termite islands," which have been gradually built up from the 

 broken-down remains of termitaries. Nor should it be forgotten that 

 the white ants are often used as food. On the other hand, Escherich 

 does not hesitate to rank them as among the great hindrances to the 

 spread of civilisation. They insidiously devour everything wooden, 

 from the telegraph-post to the wooden butt of the gun hanging against 

 the wall, from books in the library to corks in the cellar. There does 

 not seem sufficiently precise information in regard to the Uving plants 

 that they attack, and no safe general statement can be made except 

 that their appetite is large and cathohc. 



With a centre in earthworms, what a variety of interests must be 

 included within the radius of their Ufe and work! — centipedes, birds, 

 moles, seedlings, man. The same is true of termites, and two further 

 illustrations may be given. Observers have reported about thirty 

 different species of termites with the habit of feeding on fungi grovni 

 within the termitary on specially constructed mazy beds. The habit 

 is interesting in many ways; for instance, because the fungi afford 

 a supply of nitrogenous material which is scarce in the ordinary diet 

 of wood, and also because a similar habit occurs in the quite unrelated 

 true ants. Finally, the web is illustrated by the numerous boarders, 

 mostly beetles, that are found in the termitaries — not hostile intruders 

 or parasites, but guests which are fed and cared for apparently for the 

 sake of a palatable exudation with a pleasant, narcotising effect on the 

 termites. With a centre in termites, what a variety of interests must 

 we not include within the radius of their life and work! — fungi and 

 trees, beetles and birds, lizards and anteaters, and man more than any. 



The hand of life upon the earth. — The hand of life has been 

 working upon the earth for untold ages. Take plants, for instance. 

 The seaweeds lessen the force of the waves, the lichens eat into the 



