93 Prof. A. Gray on Species considered as to 



gress of erection, the superstructure is altered by his successors, like 

 the Duomo of Milan from the Roman to a different style of archi- 

 tecture." 



Entertaining ourselves the opinion that something more than 

 natural selection is requisite to account for the orderly produc- 

 tion and succession of species, we offer two incidental remarks 

 upon the above extract. 



First, we find in it, in the phrase "natural selection, or a 

 process of variation from external influences," an example of 

 the very common confusion of two distinct things, viz. variation 

 and natural selection. The former has never yet been shown to 

 have its cause in "external influences," nor to occur at random. 

 As we have elsewhere insisted, if not inexplicable, it has never 

 been explained : all we can yet say is, that plants and animals 

 are prone to vary, and that some conditions favour variation. 

 Perhaps in this Dr. Falconer may yet find what he seeks : for 

 "it is difficult to believe that there is not in [its] nature a 

 deeper-seated and innate principle, to the operation of which 

 natural selection is merely an adjunct." The latter, which is 

 the ensemble of the external influences, including the competi- 

 tion of the individuals themselves, picks out certain variations 

 as they arise, but in no proper sense can be said to originate 

 them. 



Secondly, although we are not quite sure how Dr. Falconer 

 intends to apply the law of phyllotaxis to illustrate his idea, we 

 fancy that a pertinent illustration may be drawn from it in this 

 way. There are two species of phyllotaxis, perfectly distinct, 

 and, we suppose, not mathematically reducible the one to the 

 other, — viz. (1), that of alternate leaves, with its varieties; and 

 (2) that of verticillate leaves, of which opposite leaves present 

 the simplest case. That, although generally constant, a change 

 from one variety of alternate phyllotaxis to another should occur 

 on the same axis, or on successive axes, is not surprising, the 

 different sorts being terms of a regular series — although, in- 

 deed, we have not the least idea as to how the change from the 

 one to the other comes to pass. But it is interesting, and in 

 this connexion perhaps instructive, to remark that, while some 

 dicotyledonous plants hold to the verticillate {i. e. opposite- 

 leaved) phyllotaxis throughout, a larger number (through the 

 operation of some deep-seated and innate principle, which we 

 cannot fathom) change abruptly into the other species at the 

 second or third node, and change back again in the flower, or 

 else effect a synthesis of the two species in a manner which is 

 puzzling to understand. Here is a change from one fixed law 

 to another, as unaccountable, if not as great, as from one specific 

 form to another. 



