THE HEREDITY OF RICHARD ROE. 



125 



Out of these elements Mr. Galton frames the idea of a 



" mid-parent," a sort of centre of gravity of heredity, 



which in language, not algebra, would 

 The mid-parent. ^ ^, ^ . , ^ 



represent the same set of ideas. But, as 



Dr. Brooks has observed, " It may be well to ask what 

 evidence there is that the child does inherit from any 

 ancestor except its parents, for descent from a long line 

 of ancestors is not necessarily equivalent to inheritance 

 from them, and it is quite possible that the conception 

 of a 'mid-parent' may be nothing but a logical abstrac- 

 tion." * The parents of Richard Roe were his father and 



fact. In each process of generation, half these qualities, al- 

 ready once divided, are lost or rendered unrecognisable by indi- 

 vidual variations or by contradictory blendings. To each parent 

 Galton assigns about twenty-five per cent of these personal 



B B' 



qualities. Accepting this as approximate, — + — would be nearer 



the actual fact, and we may so take it. But the latent influence 

 of the grandparents must come in, these represented by C, C, C", 

 and C" respectively. In this case the divisor may apparently 

 be 16, which corresponds to Galton's estimate of 6§ per cent. 

 Should we wish to go farther back, the influence of the great- 

 grandparents, D, D' D", etc., eight of them, could be added, each 

 with 64 as its divisor. 



It is evident that these divisors are all proximate only, and 

 varying at each cleavage of the germinal chromatin. The un- 

 known and fluctuating element in this division we may designate 



as ± n. Hence would represent the direct heritage of his 



4 ± « 



father to Richard Roe. Then A 4- — ; — + — , 1- -r-; — o-f 



4 ± « 4 ± w 16 ± «* 16 ± «* 



C" C" 8Detc. 16 E etc. 



-H -r~; — 9 + "^"; — 9+7 — ; — -I 7 — ; — i, etc., will be our first rough 



16 ± «* 16 ± «* 64 ± n 256 ± n* ° 



draft of the hereditary framework of Richard Roe. 



* In that case the formula given in the above note would be 



modified to this extent. The value of C, D, E, etc., would be 



limited to the hereditary characters latent but undeveloped in B, 



etc. Their value would be less than B, for some part of B would 



