330 



long attended to the habits of humble-bees, believes that ' more than two-thirds 

 of them are thus destroyed all over England.' Now the number of mice is 

 largely dependent, as every one knows, on the number of cats ; and Mr. 

 Newman says, ' Near villages and small towns I have found the nests of 

 humble-bees more numerotis than elsewhere, which I attribute to the number 

 of cats that destroy the mice.' Hence it is quite credible that the presence of 

 a feline animal in large numbers in a district might determine, through the 

 intervention first of mice, and then of bees, the frequency of certain flowers 

 in that district ! " 



In summing up the results of his enquiries, Mr. Darwin has applied the 

 term " Natural selection " to the principle or operative agency, which the 

 foregoing extracts are intended to illustrate, viz., that principle under which 

 slight variations in any species tend, if useful, to be accumulated and to be 

 preserved to succeeding generations. The term " Natural selection " was 

 adopted by Mr. Darwin in order to mark the relation of the principle or 

 agency in question, to the power which man exercises over domestic animals, 

 for, as you are aware, man by taking advantage of variations in character 

 amongst domesticated animals has been able to produce a large number of 

 breeds and varieties, more or less useful to himself. It must not, however, be 

 supposed that nature operates as rapidly or necessarily in the same direction as 

 man in assimilating such variations. 



"Man," says Mr. Darwin in his work on "Animals and Plants under 

 Domestication," " selects varying individuals, sows their seeds, and again 

 selects their varying offspring. He may be said to be trying an experiment on 

 a gigantic scale, but the initial variation on which he works, and without 

 which he can do nothing, is caused by slight changes in the conditions of life 

 which must often have occurred under nature. The experiment which man 

 has been making is one which nature, during the long lapse of time, has 

 incessantly tried." 



To sum up again : I have now briefly shown you — by reviewing 

 the investigations of modem writers on such subjects, and chiefly those 

 of Hooker, Lindley, Darwin, Lyell^ and Marsh, — -the divisions and sub- 

 divisions of the organic world ; the laws which regulate the geographical 

 distribution of plants and animals ; the tendency to vary which characterises 

 living organisms ; the principles under which any vai'iation, however slight, 

 and from whatever cause proceeding, if it be profitable, tends to the preserva- 

 tion of the individual ; the trans missibility of acquired variations in character ; 

 and the struggle for existence which all life is engaged in. 



And I have also shortly called your attention to the distribution, affinities, 

 and general characteristics of the Flora and Fauna of these Islands — sketchily 

 it is true— but sufficiently for the purposes of my further observations, if, as I 

 have a right to suppose, you have made any reasonable use of the opportunities 

 you enjoy in common with myself, of acquiring more detailed knowledge in 

 regard to them. 



It was my intention originally to have dealt with the whole of my subject 

 in this lecture, but I have found it impossible to do so, and I am compelled to 

 defer to a future occasion a consideration of the position, (relatively to the 

 questions discussed in this and in my last lecture), in which our Flora and 

 Fauna stood immediately before the systematic colonization of these islands, 

 and the effects already produced, and likely to follow, from the introduction of 

 competing foreign organisms. This, of course, I can only do broadly and 

 biiefly, but I hope to satisfy you, that the operations now going on are calcu- 

 lated to produce all the results which I have suggested as probable in the future. 



