332 PROCEEDINGS OF THE AMERICAN ACADEMY. 



made the following statement, as quoted by J. A. Thompson in his 

 " History and Theory of Heredity." * 



"Through a great series of generations the germinal protoplasm re- 

 tains its specific properties, dividing in every reproduction into an 

 ontogenetic portion, out of which the individual is built up, and a 

 phylogenetic portion, which is reserved to form the reproductive 

 material of the mature offspring. This reservation of the phylo- 

 genetic material I described as the continuity of the germ protoplasm. 

 Eucapsuled in the ontogenetic material the phylogenetic protoplasm 

 is sheltered from external influence, and retains its specific and em- 

 bryonic characters." f 



In 1880 M. Nussbaum $ substituted a new hypothesis for Darwin's 

 pangenesis. According to the view of this observer, the germinal cells 

 from which the sexual products are derived are separated off from the 

 other cells of the embryo very early, and undergo little alteration. 

 Hence he concluded that some of the original germ substance is di- 

 rectly abstracted from the egg, and preserved without essential altera- 

 tion to become, by giving rise to the sexual elements, the germ substance 

 of another generation. Nussbaum also expressed his disbelief in the 

 transmission of acquired characters. This belief, held by Darwin as 

 well as by Lamarck, and almost universally adopted by medical men, 

 had not before been called in question. 



In 1884 Nageli § took the ground that there are in every living cell 

 two substances ; one the nutritive plasm, and the other his hypothetical 

 " idioplasma." This view was indorsed by Kolliker, who claimed that 

 the sharp distinction between body and germ cells does not exist. 



* Proc. Royal Society Edinburgh, 1889, pp. 91-116. See also Brooks, " The 

 Law of Heredity," 1883; Osborn, "The Cartwright Lectures," 1892; " Present 

 Problems in Evolution and Heredity," Medical Record, New York, 1892; "The 

 Present Problem of Heredity," Atlantic Monthly, March, 1891. 



t Lehrbuch der algemeinen Zoologie, Leipzig, 1878, II. Abtheilung. In a 

 previous book, published at an earlier date than the one quoted by Thompson, 

 Zoologische Briefe, Wien, 1876, Jaeger writes thus : " Hier muss ich noch einmal 

 den Gegensatz zwischen Darwin's Theory von der Pangenesis und meiner 

 Theorie von der Continuitat des Keimprotoplasmas hervorheben " (p. 326). 



See also Weismann, " The Germ Plasm," p. 200. The author appears to 

 have overlooked the statement of Jaeger in his Zoologische Briefe, wherein he 

 explicitly, as shown by our quotation, refers to the "continuity of the germ 

 protoplasm." 



| Die Differenzirung des Geschlechts in Thierreich. Archiv fiir mikroskop. 

 Anatomie, Bd. XVIII., 1880. 



§ Nageli, Mechanisch-physiologische Theorie der Abstammungslehre. Miin- 

 chen u. Leipzig, 1884. 



