244 . Form and Color in Nature. 



tation of those primary membranes which, are their usual 

 agencies. 



There is every reason to believe that these senses also 

 were gradually developed through the reaction of the indi- 

 vidual to the environment, as has been described in the case 

 of the sense of sight. 



You will hardly expect me to go through all the argu- 

 ments for the credibility of the development theory. This 

 straw has already been threshed over among us many times, 

 and the belief in the theory is now so universal among sci- 

 entific men that it seems as useless to enter into argument 

 upon it as to attempt to wrestle with Brother Jasper. That 

 there are many differences in the manner in which this 

 theory is accepted among scientific men is most true. Cope 

 is opposed to Wallace, and Eimer to Weissman ; the strict 

 Darwinian out-Darwins Darwin, and some of the neo-La- 

 marckians hark back of them all. And as to pretty nearly 

 all alike, we sometimes feel that in their arguments it is 

 " heads, I win ; tails, you lose," so ready are they to account 

 for apparent exceptions to their rules. It is somewhat as 

 in the management of the restless child after trying in 

 vain to keep it in its place they say : " Then get up and run 

 about, for I will be minded." 



Sometimes it seems to us that their difficulty consists in 

 being too near to the subjects of their investigation ; they 

 are like our venerated friend Yankee Doodle, of whom it is 

 said, as you will remember, that " he could not see the town 

 for so many houses." 



For myself, as a sympathetic pupil and not an original 

 investigator, I may say that, after a pretty wide survey of 

 the field and of the evidence adduced, my leaning is toward 

 the later Darwin and, measurably, the neo-Lamarckians. 



As you are doubtless aware, the main contention is around 

 the question whether natural selection has been practically 

 the sole agent in the modification of species, or whether 

 some considerable credit is also to be given to use and dis- 

 use and to inheritance. There is also a struggle over the 

 question whether there is an inherent tendency to vary in a 

 certain direction. 



Lamarck's principal cause for the development of species 

 was functional activity and habit, acquired in adaptation to 

 environment and fixed by inheritance. Darwin realized 

 and pictured the intensity of the struggle for existence 

 which inevitably results from the immense productivity of 



