64 



THE AMERICAN ENTOMOLOGIST. 



phenomena lying on the border-land be- 

 tween them, to escape entirely. 



It is an old truth that many animals 

 subsist on vegetables. It is a newer truth 

 that all animals depend altogether, either 

 directly or indirectly, upon plants. It is 

 a still newer truth that many plants are 

 partially or wholly dependent for their ex- 

 istence on certain animals. 



The power of plants to manufacture 

 protoplasm and starch has no parallel in 

 animal physiology. Viewed from their 

 relations to the inorganic world plants are 

 producers while animals are parasites. 



True, there are organisms which, from 

 morphological considerations, are called 

 plants, but which are also parasites. And 

 there are other organisms which have been 

 and still are called animals, but which 

 originate organic matter. But these are 

 only illustrations of the difficulty in at- 

 tempting to preserve popular names which 

 were applied to things before science had 

 taught us the nature of the things them- 

 selves. And this question of names is still 

 further complicated by cases in which both 

 functions are performed by the same in- 

 dividual. We may remand Volvox and the 

 Bacteria to the vegetable kingdom and the 

 fungi to the animal, but what shall we do 

 with the mistletoe, the pine-sap, and the 

 broom-rape ? The terms " animal " and 

 " plant " do not express the fundamental 

 distinction which nature makes between 

 the two departments of life ; and when we 

 attempt to define that distinction by say- 

 ing that the true vegetal function is 

 chemical while the true animal function is 

 physiological, the terms thus employed must 

 be taken in a special scientific sense and 

 not in the popular acceptation. Giving 

 them this sense we can correctly say that 

 there are large groups of organisms in 

 which both animal and vegetal functions 

 are performed by the same individual, 

 whose reference to the one or the other 

 of the two kingdoms is a pure matter of 

 convenience, to be determined chiefly by 

 morphological considerations. Still cling- 

 ing to our definition, we may also correctly 

 declare that all animals subsist exclu- 



sively on the products of vegetation. They 

 are parasites in the highest sense, fully 

 installed parasites, the respectable ruling 

 classes, who never think of work. The so- 

 called parasitic plants, on the other hand, 

 are degenerate tramps who combine a 

 little drudgery with much unsystematic 

 plunder, thus rendering themselves un- 

 popular. And it may be generally stated 

 that the tendency of all life is to escape 

 this drudgery of organic production 

 wherever an opportunity presents itself, 

 and this it does even where great degen- 

 eracy is the necessary result.* I certainly 

 need not point out here the parallel be- 

 tween the two great sciences of Biology 

 and Sociology. 



Leaving these general considerations 

 relative to the fundamental dependence 

 of animal upon vegetable life, I propose to 

 call attention to some facts of a more 

 practical nature coming under the same 

 head. 



It is of course chiefly as food that 

 animals appropriate plants ; but there are 

 many and varied ways in which this takes 

 place, and the extent to which certain ani- 

 mals are nourished by certain plants exerts a 

 great influence upon both the floras and 

 faunas of the various regions of the globe, 

 thus bearing directly upon the problems 

 of geographical distribution. The intro- 

 duction of a new animal into a region in 

 which it did not previously exist often so 

 greatly alters the vegetation in a few years 

 that it would scarcely be recognized. Such 

 an effect has been produced in South Am- 

 erica by the introduction of horses which 

 have become wild and now roam in great 

 numbers over the pampas. And even 

 small animals produce effects which seem 

 quite out of proportion to the cause. The 

 operations of man in changing the face of 

 Nature, when scientifically viewed, consti- 

 tute an illustration of the same truth. Of 

 all the migratory animals man exerts the 

 most profound influence upon the flora of 

 the globe. He not only exterminates cer- 

 tain species and fosters others, as do other 



* Ernst Haeckel, Ueber de Individiuiliiat des Thierkor- 

 pers, pp. 10, H. 



