PACKARD. — INHERITANCE OF ACQUIRED CHARACTERS. 331 



XV. 



ON THE INHERITANCE OF ACQUIRED CHARACTERS IN 

 ANIMALS WITH A COMPLETE METAMORPHOSIS. 



By Alpheus S. Packard, M. D 



Presented January 10, 1S94. 



I. The Physical Basis of Heredity. 



Before discussing our subject it may be well to give a brief histori- 

 cal sketch of the present views as to the physical basis of heredity. 



As early as 1849. Owen, in his "Comparative Anatomy," suggested 

 that there was a physical basis for heredity. Herbert Spencer, in his 

 "Principles of Biology" (1866), based the phenomena of heredity on 

 the supposed presence of " physiological units," which he conceived to 

 be immensely more complex than chemical units or molecules. (Vol. 

 I. p. 183.) But Darwin in 1868 brought the question to the front in 

 his " Hypothesis of Pangenesis," which was disproved by experiments 

 on the effects of transfusion of blood by Francis Galton,* who in 

 1875 published a theory of heredity which in some ways approached 

 that of Jaeger. 



Galton also claimed that acquired characters are only " faintly heri- 

 table," and he endeavors to explain the almost complete non-trans- 

 mission of acquired modifications, f 



The first, however, to suggest an objective and scientific basis 

 appears to have been Dr. G. Jaeger, of Germany, who in 1876 



* Galton in 1875 suggested that each individual may properly be conceived 

 as consisting of two parts, one of which is latent, and only known to us by its 

 effects on posterity, while the other is patent, and constitutes the person manifest 

 to our sense. "He also claimed that we are made up bit by bit of inherited 

 structures, like a new building composed of the fragments of an old one, — 

 one element from this progenitor, another from that, although such elements 

 are usually transmitted in groups." — A Theory of Heredity, Journal of the 

 Anthropological Institute, 1875. See also Contemporary Review, December, 

 1875. 



t Contemporary Review, 1875, Vol. XXIII. p. 95. 



