316 THE SIGNIFICANCE OF SEXUAL REPRODUCTION 



of pangenesis is right, and that the gemmules really circulate in 

 the body, accompanied by other gemmules from the diseased parts 

 of the brain, and that some of these latter pass into the germ- 

 cells of the individual, to what strange results would the further 

 pursuit of this idea lead ? What an incomprehensible number of 

 gemmules must meet in a single sperm- or germ-cell, if each of 

 them is to contain a representative of every molecule or group 

 of molecules which has formed part of the body at each period of 

 ontogeny. And yet such is the unavoidable consequence of the 

 supposition that acquired molecular states of certain groups of cells 

 can be transmitted to the offspring. This supposition could only be 

 rendered intelligible by some theory of preformation 1 , such as Dar- 

 win's pangenesis ; for the latter theory certainly belongs to this 

 category. We must assume that each single part of the body at 

 each developmental stage is, from the first, represented in the germ- 

 cell as distinct particles of matter, which will reproduce each part 

 of the body at its appropriate stage as their turn for development 

 arrives. 



I will only briefly indicate some of the inevitable contradictions 

 in which we are involved by such a theory. One and the same 

 part of the body must be represented in the germ- or sperm-cell 

 by many groups of gemmules, each group corresponding to a 

 different stage of development ; for if each part gives off gem- 

 mules, which ultimately reproduce the part in the offspring, it is 

 clear that special gemmules must be given off for each stage in 

 the development of the part, in order to reproduce that identical 

 stage. And Darwin quite logically accepts this conclusion in his 

 provisional hypothesis of pangenesis. But the ontogeny of each 

 part is in reality continuous, and is not composed of distinct and 



1 It is generally known that the earlier physiologists believed in what was called 

 the ' evolutionary theory,' or the ' theory of preformation.' This assumes that the 

 germ contains, in a minute form, the whole of the fully- developed animal. All the 

 parts of the adult are preformed in the germ, and development only consists in the 

 growth of these parts and their more perfect arrangement. This theory was generally 

 accepted until the middle of the last century, when Kaspar Friedrich Wolff brought 

 forward the theory of ' epigenesis,' which since that time has been the dominant one. 

 This assumes that no special parts of the germ are preformations of certain parts of 

 the fully-developed animal, and that these latter arise by a series of changes in the 

 germ, which gradually gives rise to them. In modern times the theory of preforma- 

 tion has been revived in a less crude form, as is shown by the ideas of Niigeli, and 

 by Darwin's 'pangenesis.' A. W., 1888. 



