34 THE KINGDOM OF MAN 



some regions exterminated big game, have per contra 

 been introduced by man through his importation of 

 diseased animals of his own breeding from Europe. 

 Most, if not all, animals in extra-human conditions, in- 

 cluding the minuter things such as insects, shell-fish, 

 and invisible aquatic organisms, have been brought 

 into a condition of 'adjustment' to their parasites as 

 well as to the other conditions in which they live : it 

 is this most delicate and efficient balance of Nature 

 which Man everywhere upsets. A solitary case of a 

 ravaging epidemic constantly recurring amongst animals 

 living in extra-human conditions, one of a strangely 

 interesting character, is the phosphorescent disease of 

 the sand-shrimps or sand-hoppers. This is due to a 

 microscopic parasite, a bacterium, which infests the 

 blood and is phosphorescent, so that the infected sand- 

 hopper has at night the brilliancy of a glow-worm. 

 The disease is deadly, and is common among the sand- 

 hoppers dwelling in the sandy flats of the north coast 

 of France, where it may readily be studied. 1 It has 



cited, is brought about by man's importations and exportations of useful 

 plants. He thus brought the Phylloxera to Europe, not realizing before 

 hand that this little parasitic bug, though harmless to the American 

 vine, which puts out new shoots on its roots when the insect injures the 

 old ones, is absolutely deadly to the European vine, which has not 

 acquired the simple but all-important mode of growth by which the 

 American vine is rendered safe. Thus, too, he took the coffee-plant to 

 Ceylon, and found his plantations suddenly devastated by a minute 

 mould, the Himileia vastatrix^ which had lived very innocently before 

 that in the Cingalese forests, but was ready to burst into rapacious and 

 destructive activity when the new unadjusted coffee-trees were imported 

 by man and presented in carefully crowded plantations to its unre- 

 strained infection. 



1 The phosphorescent disease of the sand-hopper (Talitrus) is de- 

 scribed by Giard and Billet in a paper entitled * Observations sur la 

 maladie phosphorescente des Talitres et autres Crustaces,' in the 

 memoirs of the Societe de Biologic, Oct. 19, 1889. Billet subsequently 



