PACKARD. — INHERITANCE OF ACQUIRED CHARACTERS. 307 



first explanation which would suggest itself to any observer. On the 

 other hand, the extremely complicated speculative and a priori second 

 explanation of Weismann, based as it is on pure assumptions, does not 

 carry conviction, and thus is not an efficient working hypothesis to 

 explain inheritance at corresponding periods of life. 



It is noticeable that in his writings Weismann does not touch upon 

 homochronous heredity, though his earlier work, "Studies in the The- 

 ory of Descent" (187G), which is largely based on Lamarckian view.-, 

 afterward abandoned by the author, is a storehouse of the most sug- 

 gestive facts. 



In seeking to explain the causes of a metamorphosis in animals, 

 one is compelled to go back to the primary factors of organic evolu- 

 tion, such as the change of environment, whether the factors be cos- 

 mical (gravity), physical changes in temperature, effects of increased 

 or diminished light and shads, under or over nutrition, and the changes 

 resulting from the presence or absence of enemies, or of isolation. 

 The action of these factors, whether direct or indirect, is obvious, 

 when we try to explain the origin or causes of the more marked meta- 

 morphoses of animals. Then come in the other Lamarckian factors 

 of use and disuse, new needs resulting in new modes of life, habits, 

 or functions, which bring about the origination, development, and 

 perfection of new organs, as in new species and genera, etc., or which 

 in metamorphic forms m ly result in a greater increase in the number 

 of, and an exaggeration of the features characterizing the stages of 

 larval life. 



VI. The Adequacy of Neolamarckism:. 



It is not to be denied that in many instances all through the cease- 

 less operation of these fundamental factors there is going on a process 

 of sifting or of selection of forms best adapted to their surroundings, 

 and best fitted to survive, but this factor, though important, is quite 

 subordinate to the initial causes of variation, and of metamorphic 

 changes. 



Neolamarckism,* as we understand this doctrine, has for its founda- 



* In 1885, in the Introduction to the " Standard Natural History," we proposed 

 the term Neolamarckianism, or Lamarckism in its modern form, to designate the 

 series of factors of organic evolution, and we take the liberty to quote the pas- 

 sage in which the word first occurs. We may add that the briefer form, Neo- 

 lamarckism, is the more preferable. 



"In the United States a number of naturalists have advocated what may be 

 called Neo-Lamarckian views of evolution, especially the conception that in 



