August 6, 1886.] 



SCIEJSrCE. 



129 



Professor Weismann °" has adopted Nussbaum's 

 conception, and defended it with considerable 

 energy, adding also several important modifica- 

 tions. Nussbaum pointed out that there is note- 

 worthy evidence in the development of various 

 animals, tending to show that 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 sub- 

 stance is directly abstracted fi-om the ovum, and 

 preserved without essential alteration to become, 

 by giving rise to the sexual elements, the germ 

 substance of another generation. Weismann in- 

 sists upon the corollary, that the whole nature of 

 the animal or plant depends upon its germinal sub- 

 stance, and that the reason why the offspring is like 

 the parent is that in each biont some of the germinal 

 matter is preserved unchanged. He calls this view 

 the theory of the continuity of germ plasma. He 

 follows Nussbaum also in emphasizing the fact 

 that this theory is inconsistent with the theory 

 of pangenesis and with the theory of the trans- 

 mission of parental characteristics which are 

 acquired through external causes. On these 

 two points Weismann's second and third papers 

 mentioned in the footnote -° are the most impor- 

 tant. I fully coincide with him as regards pan- 

 genesis, but am less inclined to do the same as re- 

 gards acquired characteristics. It is upon the lat- 

 ter theme that Virchow has opposed him. I am 

 compelled to say, however, that the distinguished 

 pathologist has failed to understand Weismann's 

 position correctly, and that most of his criticisms 

 I cannot deem valid. 



According to the theory of Nussbaum and Weis- 

 mann, the cells in the embryo separate into two 

 kinds, - — 1°, the germ cells, which are converted 

 into the sexual elements ; and, 2°, the somatic 

 cells, which constitute the body of the organism. 

 The germ cells descend directly from the impreg- 

 nated ovum, and undergo little alteration, so that 



20 Weismann's first paper was read before the University 

 of Freiburg as a Prorectorats Rede, and was published in 

 pamphl(-t form at Jena in 1883, with the title ' Ueber die 

 vererbung.' A second paper was read before the German 

 Naturforscherversammlung in 1885, and appeared in the 

 Tageblatt of that association : it was subsequently ampli- 

 fied and republished with the title, 'Die coatinuitat des 

 keimplasmas,' etc. (Jena, 1885). A third paper, 'Ufberdie 

 bedeutung der gesctilechtlichen fortpflanzung fiirdie selec- 

 tionstheorie.' was likewise addressed to the Naturfor- 

 scherversammluLg, and published at Jena (IBS'!). A notice 

 of this last by KoUmanu was given in the Biolog.centralbl., 

 Y. pp. 073 and 705. At the same meeting of the Katur 

 forscher, Virchow also delivered an address (since pub- 

 lished in Virchow's archiv, ciii. pp. 1, 205, 4]3, and in shorter 

 form in the Biolog. centralbl., vi. jp. f7, ltd, and 161), in 

 which he attacked Weismann's thesis. To KoUmann and 

 Virchow, Weismann has replied (Biolog. centralbl., vi. 

 p. 33). 



they have (in suspension) the power to produce a 

 whole organism. It is difficult to agree to this 

 remarkable speculation : on the contrary, we must 

 side with Kolliker (I. c, pp. 44-46), who says that 

 a sharp division between germ cells and somatic 

 cells cannot be maintained. The feeling that there 

 is a flaw in Weismann's argumentation cannot be 

 escaped. While we recognize the ability, the great 

 ability, of his essajs, and cannot read them with- 

 out our minds appropriating much from them, we 

 remain sensible of the mysticism which zigzags 

 across his pages, now and then blurring his expres- 

 sions, and making his thought indefinite. After 

 reading his article on the ' Continuity of the germ 

 plasma,' there lingers an uncomfortable sense of 

 mental haze. I have already indicated elsewhere ^^ 

 a more comprehensive theory, which is irrecon- 

 cilable, so far as I can perceive, with the continu- 

 ity theory. My views 1 hope to defend on another 

 and more appropriate occasion. Nor is a discus- 

 sion of Nussbaum's theory essential in this article. 

 We turn, therefore, to the next point demanding 

 attention. 



Niigeli, the celebrated botanist, published in 1884 

 a large work containing a series of views reached 

 at the culmination of a remarkable career of scien- 

 tific research. The volume " has been less studied 

 than one would wish : it comprises over eight 

 hundred pages, and is decidedly abstruse. Nageli 

 is led to the theory that there are in every living 

 cell two substances, — one, which he calls idio- 

 plasma, in distinction to the other, which he 

 names the nutritive plasma. It is the idioplasma 

 alone which carries on the function of hereditary 

 transmission. We have here the definite concep- 

 tion, that the character of a special constituent of 

 living matter regulates the organization of it. In 

 other words, Nageli assumes the formative force 

 to reside in a specific material substratum, which 

 reproduces and perpetuates itself, occurs through- 

 out the oiganism, and supplies fragments of itself 

 to the genital products. The argument in support 

 of this theory is very able, and one can but join in 

 the praise which Kolliker and others have bestowed 

 upon it so cordially. The theory itself supphes us 

 for the first time with a tangible notion from 

 which to work ahead. A clew is given as to the 

 physiological process of heredity. 



Putting together all that has been said, the con- 

 clusion is evident. Nageli's hypothetical idio- 

 plasma is probably identical with the nuclear 

 chromatine of morphologists. 



21 MiNOT, — ' Organization and death,' in Proc. Amer. 

 assoc adv. sc, Ann Arbor, 1885. 



22 Meehanisch-pbysiologische theorie der abstammungs- 

 lehre, Munich, 1884 (available abstracts are given in the 

 Biolog. centralbl., iv. pp. 488 and 517). 



