1892.] NATURAL SCIENCES OF PHILADELPHIA. 467 



quently, successive germs may be thus differently impressed. In 

 this way also the molecular tendencies of the plasma of the germ- 

 cells of different individuals may be also modified simultaneously or 

 successively through the effect of enforced changes in the metabo- 

 lism of multitudes of contemporaneous adult individuals of the same 

 species, thus leading to a tendency toward concurrent or simulta- 

 neous variation of offspring in the same or a similar direction. 



" It will be seen that this is the only hypothesis which renders the 

 possibility of concurrent or simultaneous variation within the limits 

 of a species either conceivable or intelligible. It also lends itself to 

 an intelligible comprehension of the phenomena of the correlation 

 of the groAvth of parts, and it is also the only view which holds out 

 any promise of coordination with the highly ingenious and suggest- 

 ive hypothesis of Prof. Wilhelm Roux.'" 



If we now remember that, as development advances, the influence 

 of external disturbing agencies diminishes, so that it is far easier to 

 produce monstrosities or modifications at an early period of develop- 

 ment than at a later one, we see that the early steps of ontogenetic 

 processes are far more easily modifiable than the later ones, owing 

 to variations or distui'bances of the externally and internally 

 cooperative energies manifested during growth. We thus add an 

 important qualifying statement to what has preceded, and one that 

 confirms the preceding in a remarkable way, since it serves to prove 

 that the less specialized states, of ontogeny are more sensitive to dis- 

 turbing influences, than the later and more specialized ones. 



" It will be at once perceived that my hypothesis of the acquisi- 

 tion of variations and their transmission is the simplest that has 

 yet been offered. It interjects nothing hypothetical into our concep- 

 tion of the physical substratum of living organisms, except the 

 necessarily unknown and unknowable constitution of the molecular 

 factors of metabolism, and thus brought into harmony with the all- 

 inclusive doctrine of the conservation of energy." 



Prof. Miles closes his article as follows: — " Questions like these 

 must be answered, to furnish satisfactory explanation of biological 

 activities, and theories of nutrition and heredity in which energy is 

 not recognized as one of the prime factors in every vital process 

 should be received with caution, and the fallacious arguments based 

 upon them estimated at their real value." 



5Der Kampf der Theile im Organismus. 8vo., pp. VII, 244, Leipzig, 1891. 



