1892.] NATURAL SCIENCES OF PHILADELPHIA, 461 



sand into their mental eyes, has not been successfully paralleled in 

 recent times. Weismann's views, as shown above, carry with them 

 the implication of the denial of the validity, within the pale of 

 biology, of the doctrine of the conservation of energy. In that 

 they do this, they must be characterized as unscientific, since they 

 are not in harmony with the spirit of modern science. 



So great is the importance of the recognition of the principle of 

 the conservation of energy in the evolution of organic forms, that 

 it is strange that it has not been hitherto declared that it is the very 

 foundation upon which all further progress in the investigation of 

 biological evolution must proceed. 



How this principle is to be applied and extended in biological 

 research, in an experimental way in the future, it is obviously not 

 now possible to indicate in detail, but that such was the method 

 according to which Nature proceeded to evolve new forms, seems to 

 be proven by the fact that organic evolution by superposition has 

 occurred, as is shown by countless facts. If characters have been 

 superposed and intensified in their expression, as is beautifully shown 

 by the evolution of such structures as the nervous system and foetal 

 membranes, it seems that the interacting energies involved in bring- 

 ing this about have operated cumulatively. That is, that every 

 gain of surface for better respiration and nutrition, and combina- 

 tions of both, set the processes of the development of physiological 

 energy going at a greater rate of efficiency, which would accelerate 

 the process of evolution and its morphological possibilities. The 

 rates at which these energies, internally and externally developed, 

 shall interact, cannot be determined by natural selection, but by 

 growth and the motion of parts and particles dependent upon it. 



Weismann nowhere in his prolix and tedious essays, except in 

 one of the very latest answers to his critics, steps aside to con- 

 sider energy in relation to the problems he is discussing. He is 

 simply oblivious of the existence of such a thing as energy as affect- 

 ing the question before him. His facts may or may not have the 

 value he assigns them, his reason often being of the shallowest and most 

 commonplace texture, as for example, when he says : " The object 

 of this process (sexual reproduction) is to create those individual 

 differences which form the material out of which natural selection 

 produces new species." In this case he has mistaken an effect for a 

 cause, and has assigned as the object of sexuality an end or final 

 cause upon which neither he nor any other man can legitimately 



