VARIETIES IN EPIDERMIS 149 



that of knee-pads, as in the gnu and other ungulates. Some such 

 process it is legitimate to assume whether it be reckoned backwards 

 to monotremes or later levels of life-forms. We see then before 

 our eyes how tins living tissue becomes adapted in varied ways by 

 response to the stimuli of friction and pressure, and the modifications 

 thus slowly effected must, one would suppose, be transmitted to 

 offspring ultimately from the original groups with which the process 

 began, when by frequent repetition small changes of structure 

 have arisen at last. I acknowledge the limited force of the answer, 

 that this picture involves the continuance in each succeeding 

 generation of the stimuli which initiated the changes, but the fact 

 remains that ex hypoihesi the changes are there, written in tablets 

 of animal tissue, and that the making-up of an organism in course 

 of many ages is not and cannot be conceived as being governed 

 alone by tbe " tyranny," even in the good Greek sense of that word, 

 of rigid unit-characters. 



In the assumed process the correcting force of the Lamarckian 

 drill-sergeant is always at hand, as it superintends the construction 

 of tissues and parts, and I doubt if even Professor Thomson will 

 here interpose the difficulty of " correlation with useful characters," 

 for the only important functions which are invoked as the invariable 

 antecedent of these structures are the elementary habits of walking, 

 climbing or grasping objects in certain different ways, and without 

 these habits or functions there would be neither lemur, monkey nor 

 man to interest the mind of a biologist from Mars. As I am desirous 

 of condensing such replies as I can make to certain opinions of 

 opponents and objections, I will remind the reader that Professor 

 Bateson in the Jubilee Volume of 1909, pp. 100, 101, uses a metaphor 

 to illustrate his view that among the facts of nature we meet certain 

 definite structures and patterns in which we ought not, if desiring 

 rightly to interpret them, to expect to find jpurposefulness . He 

 says : ' Such things are, as often as not, I suspect rather of the 

 nature of tool-marks, mere incidents of manufacture, benefiting 

 their possessor not more than the wire-marks in a sheet of paper, 

 or the ribbing on the bottom of an oriental plate renders these 

 objects more attractive in our eyes." Metaphors are both indis- 

 pensable and delightful, they are the very salt of scientific and other 

 sober writings, but they have a rather " slim " way of betraying 

 their employers. They express at times the truth too well, and at 

 others when vague and inaccurate lead the reader right astray. 

 Thinking of this metaphor of tool marks I was in a modern church 

 the other day and saw just before me a stone pillar the pediment 

 of which was marked with oblique parallel marks of a mason's tool. 



