264 REVIEWS. 



rather the existence and raison d'etre of cross-fertilization 

 that stands in need of apology, or of explanation. 



He freely concedes that the flowers of many plants, and 

 some whole orders, are so constructed that intercrossing is for 

 them a necessity ; also that most of those which are believed 

 "to be normally self-fertilizing" because they can and do 

 fertilize themselves habitually, yet " may in some cases be 

 cross-fertilized by insects." It is admitted that the structure 

 of the latter is adapted — most variously and wondrously 

 adapted — to being fertilized by particular insects. As this 

 conies to pass in plants and flowers of the highest organiza- 

 tion and greatest specialization, Darwin and his school con- 

 clude that this is a most advantageous outcome, and means 

 some real good to the species ; that when this is accompanied 

 with a loss of self-fertility, it is the loss of something no 

 longer useful, something better than self-fertility having taken 

 its place. But Mr. Henslow, reading this the other way, 

 having determined " that self-fertilization is per se a decided 

 advantage," and free from injurious liability, comes to regard 

 intercrossing as merely " a compensatory process for the loss 

 of self -fertility." 



But how and why did this " compensatory process " come to 

 pass ? It is conceived on both sides that flowers were " pri- 

 mordially inconspicuous." (To this Henslow adds herma- 

 phrodite and self-fertile, but that need not here come into 

 account.) Both agree that insects have mainly determined 

 their conspicuousness. Darwin says this has been determined 

 through natural selection by the survival of the more and 

 more conspicuous variations, correlated with their producing 

 something srood for the insect of which the coloration was a 

 sign, and that the preferential survival of the more showy 

 and attractive was a consequence of some benefit of the inter- 

 crossing. Henslow propounds the view that insects have de- 

 termined the conspicuousness more directly, and not by bene- 

 fiting but by irritating the flowers. " These, by being greatly 

 stimulated by the repeated visits of insects, tend to become 

 hypertrophied. Hence the corolla, enlarges, becomes more 

 brightly colored, the nectariferous organs increase the quan- 



