104 NATURAL SCIENCE [August 



journey to varieties of the same species. In numerous cases I have 

 seen bees visit two, three, and even four species in the course of a 

 minute or two. The general results of ray observations on this 

 point are as follows : — 



Hive bees are much more constant than wild bees, yet they pass 

 freely from variety to variety, and not by any means rarely from 

 species to species. As to the latter, take any wild bee, and if you 

 can follow its movements for twenty visits or more, the chances are 

 something like ten to one that it will be seen to change its species 

 of flower. If we suppose that the bee of the past acted as the bee 

 of to-day, then it seems to me that in this habit alone we have a 

 complete refutation of the theory. 



Another of the foundations of the theory is the benefit supposed 

 to result from the cross-fertilisation effected by the bee in flying 

 from flower to flower. Darwin's well-known experiments on 

 cross-fertilisation point to the conclusion that the seedlings of 

 cross-fertilised plants are more numerous and vigorous than those 

 of the self-fertilised. Without wishing to throw doubt on the 

 general deductions from these experiments, I may be permitted to 

 point out that certain facts regarding fertilisation in nature render 

 them of doubtful support to the theory. First, there is the fact 

 that certain species of flowers which are habitually self -fertilised are 

 among the most numerous and vigorous of our native plants. Such, 

 for example, are Polygonum aviculare, the least visited by insects, 

 and yet the most abundant of its genus : Veronica hederaefolia, 

 one of the commonest of the veronicas, yet very seldom visited by 

 insects, as H. Midler points out : while among the geraniums, G. 

 molle and G. pwsillum, which Midler states to be the most fre- 

 quently self-fertilised, and perhaps the most common of their genus 

 with the exception of G. robertianum. Professor Henslow, indeed, 

 has sone so far as to state that " in nature whenever self-fertilisation 

 can be effected more seed is borne than by the forms requiring 

 crossing." Among the orchids again, some species exhibit the most 

 complicated arrangements for avoiding self- and securing cross- 

 fertilisation ; others exhibit equal complications for securing the 

 former and avoiding the latter. And if the inference is that the 

 contrivances in the former case were evolved because cross- 

 fertilisation was an advantage, then it follows equally that in the latter 

 case they were evolved because self-fertilisation was an advantage 

 Darwin, in accordance with his general views on cross-fertilisation, 

 believed that such self-fertilised orchids were dying out, but the 

 increased number of such now known seems to forbid this view, 

 and it is difficult to understand how such self-fertilised orchids can 

 have been evolved from a race specially fitted for cross-fertilisation 

 on the supposition that this latter method is always beneficial. 



