Jax. 1902.] BOTANICAL SOCIETY OF EDINBURGH 145 



given pedigree, are eliminated by a law that deals only 

 with average contributions, and the varying prepotencies 

 of sex in respect to different qualities are also presumably 

 eliminated." 



Assuming for the moment the correctness of this, its 

 embryological basis is furnished by the formation, etc., of 

 the primary germ-cells. The germ-eells in any embryo, 

 possessing from their mode of formation like qualities, and 

 having these and the like ancestry with that which formed 

 the embryo, these qualities are necessarily halved at the 

 following determination of sex and reduction. At the 

 close of this halving the " parental " qualities can embryo- 

 logically, under Galton's law, only be represented by at 

 most one-half, or one-quarter for each " parent," and so on 

 for each preceding generation ; for in these also primary 

 germ-cells of like characters were formed, of which one 

 gave rise to an embryo in every case. 



The line of ancestry is, of course, from and through these 

 germ-cells, and never from the embrvo or sexual veneration 

 of a preceding generation. 



But as the germ-cells associated with any given embryo 

 are all of like characters among themselves (including that 

 from which the embryo arises) on the production of eggs 

 and sperms, and the subsequent union of these with Other 

 sexual products, the result is the same as if the line of 

 ancestry had been through the embryo, so far, at anyrate, 

 as the ancestral characters are concerned. According to 

 Galton, the parental qualities are at most represented in 

 their progeny by i (^ + 4)- 



In the same way, and because between offspring and 

 grandparent there are two sets of germ-cells (in addition to 

 those still immature in the offspring) and two reductions, 

 the grandparental portions taken together can only be half 

 of the parental portions taken together, that is to say, \', 

 and so on through any number of generations. It will be 

 quite unnecessary to carry out the examination further, for 

 study of the diagram will make evident the light it throws 

 from the embryological side on Galton's law, and how it 

 furnishes this law with its basis in the facts of development. 



In his book on the " Germplasm " (English edition, p. 

 257), Weismann has adversely criticised Galton's law. His 



