(54 J. W. SLATER, ESQ., F.C.S., F.E.S., ON 



brought into play, the more likely are new forms of plants 

 and animals to be evolved. 



Dr. H. Behr, speaking of the aboriginal vegetation of 

 California, says : — " Its very variation (?'.<?., its richness hi 

 species) is a proof of a certain want of vitality, for any more 

 vigorous organism by superseding the weaker ones would 

 have produced originally the monotony developed at present 

 by the immigration of alien plants." Here an intensified 

 struggle for existence is held up not as a multiplier but as a 

 reducer of the number of species, as a cause of monotony. 

 If such is its function in our time we may surely demand 

 very good evidence before Ave admit that it can ever have 

 played the opposite part, and been chiefly or even largely 

 instrumental in producing the present multitude of organic 

 forms from a few original types. We often forget that out 

 of the almost infinite array of animal and vegetable species, 

 a multitude, perhaps the majority, are rare. Now. if it be 

 true that a rare species is one that is verging towards 

 extinction, what are we to infer? 



Passing from these general considerations to more specific 

 objections, we often find in animals organs removed from 

 their normal position and placed elsewhere We generally 

 find the organs of hearing, like those of the other special 

 senses, placed in the head. But in insects the ears, or what 

 stands in their stead, are located differently in different 

 groups. Thus the Orthoptera (locusts, cockroaches, etc.) 

 seem to have ears on their fore-legs. In other groups these 

 organs are supposed to be attached to the subcostal vein of 

 the wings. In the two-winged flies, on the contrary, the 

 power of hearing has been traced to the two little knobs, 

 called by some " balancers " or poisers, which take the place 

 of the hindwings. 



We may therefore ask how can the organs of so important 

 a sense havebeen gradually transported, by Natural Selection, 

 from one of these positions to another? What could be the 

 advantage gained at each successive step? For we must 

 remember that the advocates of Natural Selection tell us that 

 only advantageous changes are likely to be preserved or 

 handed down to posterity. 



A most familiar fact in the life-history of insects is the 

 change which most of the so-called orders undergo. On 

 being hatched out from the egg they appear in forms for the 

 most part quite unlike their parents, and it is only by a series 

 of metamorphoses (as they are usually termed), that they 



