I should never come to an end were I to attempt to exhibit the great wealth of observations now available in regard to mimicry. But this at least may be added, that isolated cases of mimicry have been found even among Vertebrates. Thus, according to Wallace, the red-and-black striped poisonous coral snake of South America (_Elaps_) is most realistically imitated by a non-poisonous snake (_Erythrolampus_) of the same region. Among birds, Wallace cites a few cases which may be regarded as mimicry, but none are known among mammals, which is not to be wondered at when we consider how very much less numerous in individuals the species are which live together on one area, and how much less likely it is that two species should be, to begin with, so near each other in size, habit, and form that the process of natural selection could bring about a deceptive degree of resemblance. Without doubt it is among insects that the conditions for mimicry are especially favourable, partly because of the enormous number of species which live together and have interrelations on the same area, even in our latitudes and much more so in the tropics, and also because of their usually great fecundity, and their rapid multiplication, both of which are factors favourable to starting and continuing the processes of natural selection. Furthermore, we have to take into account the hosts of enemies which depend wholly or in great part on insects for food, and destroy them in enormous numbers, eliminating them in inverse proportion to the perfection of their adaptation. Finally, there is the extreme susceptibility of many insects to injury. This makes it very desirable that they should have some disguise sufficient to protect them from even the first attempt at an attack, since that would in many cases prove fatal. LECTURE VI PROTECTIVE ADAPTATIONS IN PLANTS Protection against large animals--Poisons--Ethereal oils--Spines and thorns--Sharp and stinging-hairs--Felt-hairs--Position of the thorns: buckthorn--Tragacanth shrub--Prigana scrub--Alpine shrubs--Protection against small enemies--Chemical substances--Mechanical protective arrangements--Raphides--Conclusion.