26 MUSEUM ORGANISATION i 



modification of structure must be of utility to the animal or 

 plant in which it occurs, or to some ancestor of that animal 

 or plant, otherwise it could not have come into existence ; the 

 only reservation being for cases which are explained by the 

 principle which Darwin called " correlation of growth." Thus 

 the extreme natural selectionists and the old-fashioned school 

 of teleologists are so far in agreement. 



On the other hand, it is held by some that numerous 

 structures and modifications of structures are met with in 

 nature which are manifestly useless ; it is even confidently 

 stated that there are many which are positively injurious 

 to their possesssor, and therefore could not possibly have 

 resulted from the action of natural selection of favourable 

 variations. Organs or modifications when in an incipient 

 condition are especially quoted as bearing upon this difficulty. 

 But here, it seems to me, we are continually appealing to a 

 criterion by which to test our theories of which we know far 

 too little, and this (though often relied upon as the strongest) 

 is, in reality, the weakest point of the whole discussion. 



Of the variations of the form and structure of organic 

 bodies we are beginning to know something. Our museums, 

 when more complete and better organised, will teach us much 

 on this branch of the subject. They will show us the infinite 

 and wonderful and apparently capricious modifications of form, 

 colour, and of texture to which every most minute portion of 

 the organisation of the innumerable creatures which people the 

 earth is subject. They will show us examples of marvellously 

 complicated and delicate arrangements of organs and tissues in 

 many of what we consider as almost the lowest and most 

 imperfectly organised groups of beings with which we are 

 acquainted. But as to the use of all these structures and 

 modifications in the economy of the creatures that possess 

 them, we know, I may almost say, nothing, and our museums 

 will never teach us these things. If time permitted I might 

 give numerous examples in the most familiar of all animals, 

 whose habits and actions are matters of daily observation, 

 with whose life-history we are as well acquainted almost as 

 we are with our own, of structures the purposes of which are 

 still most doubtful. There are many such even in the 



