174 THE CONTINUITY OF THE GERM-PLASM AS THE 



ascertained facts agree with and can be explained by it. Moreover 

 the ceaseless activity of research brings to light new facts every 

 day, and I am far from maintaining that my theory may not be 

 disproved by some of these. But even if it should have to be 

 abandoned at a later period, it seems to me that, at the present time, 

 it is a necessary stage in the advancement of our knowledge, and 

 one which must be brought forward and passed through, whether 

 it prove right or wrong, in the future. In this spirit I offer the 

 following considerations, and it is in this spirit that I should wish 

 them to be received. 



I. THE GERM-PLASM. 



I must first define precisely the exact meaning of the termj 

 germ-plasm. 



In my previous writings in which the subject has been alluded 

 to, I have simply spoken of germ-plasm without indicating more 

 precisely the part of the cell in which we may expect to find this 

 substance the bearer of the characteristic nature of the species 

 and of the individual. In the first place such a course was sufficient 

 for my immediate purpose, and in the second place the number of 

 ascertained facts appeared to be insufficient to justify a more exact 

 definition. I imagined that the germ-plasm was that part of a 

 germ-cell of which the chemical and physical properties including 

 the molecular structure enable the cell to become, under appro- 

 priate conditions, a new individual of the same species. I therefore 

 believed it to be some such substance as Niigeli l , shortly afterwards, 

 called idioplasm, and of which he attempted, in an admirable 

 manner, to give us a clear understanding. Even at that time 

 one might have ventured to suggest that the organized substance 

 of the nucleus is in all probability the bearer of the phenomena of 

 heredity, but it was impossible to speak upon this point with any 

 degree of certainty. O. Hertwig 2 and Fol 3 had shown that the 

 process of fertilization is attended by a conjugation of nuclei, and 

 Hertwig had even then distinctly said that fertilization generally 



1 Niigeli, ' Mechanisch-physiologische Theorie der Abstaminungslehre.' Munchen 

 u. Leipzig, 1884. 



a 0. Hertwig, ' Beitriige zur Kenntniss der Bildung, Befruchtung und Theilung 

 des thierischen Eies.' Leipzig, 1876. 



3 Fol, ' Recherches sur la fecondation, etc.' Geneve, 1879. 



