INTRODUCTION 7 



Galton * was the first to make an attempt to improve on the 

 theory of pangenesis. In a short but suggestive essay he 

 accepted the hypothesis of the gemmules, but rejected the 

 doctrines of their circuhition through the blood, and of the 

 aggregation in the germ-cells of gemmules given off by the body- 

 cells. Now as the gemmules which have been converted into 

 body-cells are used up, it follows that the germ-cells can only 

 contain those gemmules which are left — those, out of the enor- 

 mous number contained in a germ-cell, which have not developed 

 further. For each germ-cell, as both Galton and Darwin assume, 

 contains each kind of gemmule in many modifications, originat- 

 ing from the different ancestors of the organism. The theory 

 of the origin of the germ-cells from the remains of the germ 

 mass not used up in ontogeny (' the residue of the stirp ') has 

 been compared to, and regarded as the precursor of, the con- 

 ception of the continuity of the germ-plasm which I originated 

 long afterwards. A certain resemblance .does, it is true, exist 

 between the two conceptions, but it will be shown in the section 

 on the continuity of the germ-plasm that the similarity is only a 

 superficial one. 



Herbert Spencer defines heredity as the capacity of every 

 plant and animal to produce other individuals of a like kind, 

 and states expressly that in this fact, which is perfectly famil- 

 iar to us, and for this reason seems to be a matter of course, 

 lies the real essence and principle of heredity, ^ the phenom- 

 ena commonly referred to it being quite subordinate mani- 

 festations.' Thus the blending of the individual ^characters'' 

 of the paretits in the children has, as a rule, been placed in 

 the foreground in considering questions of heredity, and it has 

 been overlooked that this is quite a secondary phenomenon, — 

 important no doubt in many respects, and interesting in a high 

 degree, but still only the result of a certain mode of multipli- 

 cation, i.e., sexual reproduction, and by no means an essential 

 phenomenon of heredity. Darwin recognised this distinctly, 

 and concerned himself primarily with the theoretical explana- 

 tion of individual development (ontogeny). But the majority 

 of writers on heredity, including Galton, have turned their 

 whole attention to the blending of the qualities of the parents 



* Francis Galton, ' A Theory of Heredity,' Journal of the Anthropo- 

 logical Institute, 1875. 



