396 



Mr. F. Galton on Blood-relationship. [June 13, 



sidering ; it embraces the combined effects of growth and multiplication, 

 as well as those of modification in quality and proportion, under both 

 internal and external influences. If we were able to obtain an approximate 

 knowledge of the original elements, statistical experiences would no doubt 

 enable us to predict the average value of the form into which they would 

 become developed, just as a knowledge of the seeds that were sown would 

 enable us to predict in a general way the appearance of the garden when 

 the plants had grown up ; but the individual variation of each case would 

 ©f course be great, owing to the large number of variable influences concerned 

 in the process of development. 



The latent elements in the embryonic stage must be developed by a 

 parallel, I do not say by an identical process, into those of the adult stage. 

 Therefore, to avoid all chance of being misapprehended when I collate 

 them, I will call, in the diagram I am about to give (see fig. 1, p. 398), 

 the one process "Development a" and the other "Development b." 



It is not intended to affirm, in making these subdivisions, that the em- 

 bryonic and adult stages are distinctly separated ; they are continuous, and 

 it is impossible but that they should overlap, some elements remaining 

 embryonic while others are completely formed. Nevertheless the two, 

 speaking broadly, may fairly be looked upon as consecutive. 



Again, the two processes are not wholly distinct ; on the contrary, the 

 embryo, and even the adult in some degree, must receive supplementary 

 contributions derived from their contemporary latent elements, because 

 ancestral qualities indicated in early life frequently disappear and yield 

 place to others. The reverse process is doubtful ; it may exist in the 

 embryonic stage, but it certainly does not exist in a sensible degree in 

 the adult stage, else the later children of a union would resemble their 

 parents more nearly than the earlier ones. 



Lastly, I must guard myself against the objection that though structure 

 is largely correlated, I have treated it too much as consisting of separate 

 elements. To this I answer, first, that in describing how the embryonic 

 are derived from the structureless elements^, < I expressly left room for a 

 small degree of correlation ; secondly, that in the development of the adult 

 elements from the embryonic there is a perfectly open field for natural selec- 

 tion, which is the agency by which correlation is mainly established ; and, 

 thirdly, that correlation affects groups of elements rather than the complete 

 person, as is proved by the frequent occurrence of small groups of per* 

 sistent peculiarities, which do not affect the rest of the organism, so far as 

 we know, in any way whatever. 



The ground we have already gained may be described as follows : — 



Out of the structureless ovum the embryonic elements are taken by 

 Class Representation, and these are developed (a) into the visible adult 

 individual ; on the other hand, returning to our starting-point at the 

 structureless ovum, we find, after the embryonic elements have been segre- 



