Rj-der.] OiO j-Ocl. 18, 



To the elucidation of some of the grounds upon which hypotheses of me- 

 chanical evolution may be founded I have steadily devoted attention since 



1877, in the belief, then, as now, that the only hope of the solution of 

 many of the problems presented by the phenomena of adaptation lay in 

 the direction sketched out in my first considerable essay, entitled, "On 

 the Meclianical Genesis of Tooth Forms," published in the latter part of 



1878. That essay met with no recognition amongst biologists except at 

 the hands of my distinguished friend, Prof. Cope. In England, a de- 

 servedly well-known odontologist dismissed it, in a work on dental 

 anatomy, with a characteristic British sneer and with comments that 

 showed that he had not only not read it, but that he had also utterly 

 failed to understand the grounds upon which my speculations were based. 

 That line of odontological study has since been most profitr.bly followed 

 out in much greater detail by Profs. Cope and Osborn, but there are other 

 and more definite proofs needed. Since the hard parts of animals are 

 moulded by the soft parts, and not vice versa, what is now required is some 

 evidence in the first place that hard parts do in reality suffer modification, 

 through the influence of the actions of an animal, and that Lamarck's 

 theorj^ of use proves true, as happens in the case of several thousand species 

 of fishes now living, notwithstanding the objections so glibly urged off"- 

 hand by biologists whose special studies unfit them to express an opinion 

 upon this subject. 



The cases usually appealed to to prove the modifying eflects of use are 

 too complex, and the history of their parts is not always well enough 

 known to afford conclusive evidence. In the series of cases now to be 

 presented this is not the case. The entire history of the parts, directly 

 aflected by an exceedingly simple mode of use, is known from their 

 earliest appearance until the completion of growth. The embryological, 

 morphological and physiological sides of the question are therefore ade- 

 quately represented in a simple case, and all that remains is to trace the 

 kinetic side of the subject, or that involving the expenditure of energy, in 

 order to complete the physical survey of the problem. 



I have been aware for upwards of ten years that it is probable that the 

 numerous transverse fractures in the so-called jointed or " soft rays " of 

 fishes had probably arisen as the result of the interaction of the living fish 

 and its surroundings. Only within a very recent period, however, has it 

 been possible for me to find evidence, which I believe to be incontro- 

 vertible, in proof of such a conclusion. This evidence serves to demon- 

 strate conclusively that Nature may and does make truly morphogenetic 

 experiments if we will but pursue her clews until she is literally taken in 

 the act of creating new features. As far as I am aware, the case about to 

 be described is the first one that has been recorded that servos as direct 

 proof of the doctrine that the structure of an organism may be altered by 

 the actions of the organism itself. 



The proof that the " soft rays " of fishes are normally fractured and 

 more or less completely segmented by the resultant interaction between 



