Page:The Zoologist, 4th series, vol 3 (1899).djvu/336

310 first learnt from Europeans to eat Oysters. The Australians do not, however, eat everything indiscriminately, but reject several things eaten by Europeans, as certain fish, crustaceans, or fungi; yet they feel no disgust at such things as maggots or rotten eggs, or even the contents of the intestines of animals taken in hunting.

Plants can also vary the nutrient salts they absorb according to the supply of the same. In the yew (Taxus baccata) there is frequently a replacement of calcium by magnesium. On comparing the quantities of calcium and magnesium in the ash of yews grown on lime and on gneiss, respectively, with those yielded in the case of serpentine formation, we find that magnesia preponderates considerably in weight over lime in a yew from serpentine rocks (which are in the main a compound of magnesia and silicic acid), whilst the proportion between these two salts is reversed in a yew grown upon limestone. The obvious inference from the table is that, in plants from a serpentine ground, lime is to a great extent replaced by magnesia.

Among other vagaries in animal diet may be mentioned that of Snails, who also devour insects, particularly Coleoptera. On the other hand, the operation is sometimes reversed. M. Flaminio Baudi found Cychrus cyclindricollis feeding on the body of Helix frigida; and Mr. Trovey Blackmore had observed Carabus stenocephalus to feed on the abundant Snails in Morocco.

Such facts as these tend to prove that a fauna is not happy by having no history, as is so often and so easily imagined; but rather that its history is like that of a continental humanity—one series of wars, attack not on all sides at once, but ever recurring from one quarter or another. The friend of to-day may have been the enemy of a long ago. Environmental changes may have produced, by a scarcity of usual food, a change of diet, and then a race of animals hitherto enjoying a comparative immunity from attack may suddenly become almost annihilated by unexpected foes. Thus we may now find an inherited mimetic resemblance