[95] THE EVOLUTION OF THE FINS OF FISHES. 1075 



breaks in those adjaceut, for the reasou that a break in one wonhl weaken 

 the support of the rays on either side. 



The efficiency of physical forces as the causes of such phenomena no 

 reasonable investigator can for an instant doubt, and to cry out against 

 such a mechanical or kinetic process of evolution as here supposed, 

 which has been assumed by critics not to convey any information, is to 

 do no more than reject the truth ; while to put natural selection in its 

 place is not only illogical but absolutely' absurd, because this mechanical 

 method of developing the segments of the rays of Teleosts is repeated 

 in exerj young fish the adult of which has segmented, well-ossified, 

 branched rays. Survival of the fittest, or natural selection, has nothing 

 to do with the process here under discussion, because whether the fish 

 survives or not to become adult, the fracturing and segmenting of the 

 rays has already happened by the time the rays are fairly formed, and 

 when the animal is only fifteen days old, and is still very far from ma- 

 ture or in condition to transmit to its offspring the disposition to seg- 

 ment the fin-rays. It might be urged in objection that the disposition 

 or the structural conditions favoring this mode of segmentation of the 

 rays was inherited. Granting even that much, it does not dispose of 

 the fact that the segmentation or fracturing is veritably caused by the 

 mechanical resistance offered to the fins when the young animal, with 

 developing permanent fin-rays, moves the latter. Moreover, it is un- 

 doubtedly true that the period when this segmentation occurs in the 

 rays of the very young fish, the latter does not represent an older an- 

 cestral type, for the reason that the degree of rigidity caused by the 

 extent to which ossific deposits are laid down during farther growth 

 determines the number or frequency of the points of fracture, which 

 increase in number with the advance in age. 



XVI. — Lamarck's shake in the development of the princi- 

 ples OF DYNAMICAL EVOLUTION. 



As Darwin and Haeckel have truly said, Lamarck is the real author 

 of the doctrine of the evolution of organisms or the theory of the trans- 

 mutation of species, as effected by the operation of natural causes con- 

 trolled by natural law. Others before or shortly after him seem to have 

 had some sort of dim conception of the same thing, but let us note how 

 forcible and pregnant some of his ideas were which he put forth in the 

 introduction to his great work entitled Histoire naturelle des Animanx 

 sans Yertehres.* 



On page 14 of that Introduction these fundamental principles find a 

 place : 



" First principle : Every fact or phenomenon of which observation 

 makes us cognizant is essentially physical, and owes its existence or 

 production to some body or to the relations between bodies." 



* Tome I, Brnxelles, 1837, 3cl editiou, revised by Deshayes and H. Milne-Edwards. 



