334 The Siudy of Animal Life PART iv 



strong, and his dismissal of Lamarckian theory is so 

 emphatic, that I shall select one of his illustrations by way 

 of contrasting his theory with that of Lamarckians. 



Many blind fishes and crustaceans are found in caves. 

 Lamarckians assume, as yet with insufficient evidence, that 

 the blindness is due to the darkness and to the disuse 

 of the eyes. Changes thus produced are believed, again 

 with insufficient evidence, to be transmitted and increased, 

 generation after generation. This is a natural and simple 

 theory, but it is not a certain conclusion. 



What is Prof. Ray Lankester's explanation ? 



" The facts are fully explained by the theory of natural 

 selection acting on congenital fortuitous variations. Many 

 animals are born with distorted or defective eyes whose 

 parents have not had their eyes submitted to any peculiar 

 conditions. Supposing a number of some species of Arthro- 

 pods or fish to be swept into a cavern, those individuals with 

 perfect eyes would follow the glimmer of light and eventually 

 escape to the outer air, leaving behind those with imperfect 

 eyes to breed in the dark place. In every succeeding 

 generation this would be the case, and even those with 

 weak but still seeing eyes would in the course of time 

 escape, until only a pure race of eyeless or blind animals 

 would be left in the cavern." This is a possible explanation, 

 but it is not a certain conclusion. 



(5) The argument which I would urge most strongly is 

 based on general physiological considerations. It gives 

 no demonstration, but it seems to establish a presump- 

 tion against Weismann's conclusion. He maintains that 

 functional and environmental changes in the body cannot 

 be transmitted because such changes cannot reach the 

 stable and to some extent insulated reproductive elements. 

 But this cannot requires proof, just as much as the converse 

 can. 



The organism is a unity ; cell is often linked to cell by 

 bridges of living matter ; the blood is a common medium 

 carrying food and waste ; nervous relations bind the whole 

 in harmony. Would it not be a physiological miracle if the 

 reproductive cells led a charmed life unaffected even by 



