574 THE PROBLEMS OF HEREDITY AND THEIR SOLUTION. 



case is that of a cross between a rich crimson magenta Chinese prim- 

 rose and a clear white, giving- a flower of a color appropriately 

 described as a " washy" magenta. 



(3) The crossbred may present some form (juite different from that of 

 either pure parent. Thougli, as has been stated, nothing can be pre- 

 dicted of an unlvnown case, we already know a considerable nmnber 

 of examples of this nature in which the nuile form approaches some- 

 times with great accuracy to that of a putative ancestor, near or 

 remote. It is scarcely possible to doubt that several — though perhaps 

 not all — of Darwin's "reversions on crossing" were of this nature. 



Such a case is that of the "wild gray mouse" produced by the 

 union of an albino tame mouse and a piebald Japanese mouse." 

 These "reversionary" mice bred together produce the parental tame 

 types, some other types, and "reversionary" mice again. 



From what has lieen said it will now be clear that the applicability 

 of the Mendelian hypothesis has, intrinsically, nothing whatever to 

 do with the question of the inheritance being blended or alternative. 

 In fact, as soon as the relation of zygote characters to gamete charac- 

 ters is appreciated, it is difficult to see any reason for supposing that 

 the manifestation of characters seen in the z3"gotes should give any 

 indication as to their mode of allotment among the gametes. 



On a previous occasion I pointed out that the terms "heredity" 

 and "inheritance" are founded on a misapplication of metaphor, and 

 in the light of our present knowledge it is becoming clearer that the 

 ideas of "transmission" of a character by parent to offspring, or of 

 there being any "contri])ution" made ])y an ancestor to its posterity, 

 must only be admitted under the strictest reserve, and merely as 

 descriptive terms. 



We are now presented with some entirely new conceptions: 



(1) The purity of the gametes in regard to certain characters. 



(2) The distinction of all zygotes according as they are or are not 

 formed by the union of like or unlike gametes. In the former case, 

 apart from variation, they breed true when mated with their like; in 

 the latter case their offspring, collectively, will be heterogeneous. 



(3) If the zygote be formed by the union of dissimilar gametes, we 

 may meet the phenomenon of (a) dominant and recessive charac- 

 ters; {h) a 1)lend form; (e) a form distinct from either parent, often 

 reversionary.'' 



«See von Guaita, Ber. Naturf. Ges. Freiburg, X, 1898, and XI, LS99, quoted by 

 Professor Weldon (see later). 



'' This fact sufliciently indicates the difficulties involved in a superficial treatment 

 of the plienomenon of reversion. To call such reversions as those named above 

 "returns to ancestral type" would In-, if more than a descriptive phrase were 

 intended, (juite misleading. It is not the ancestral type that lias come back, but 

 something else has come in its guise, as the offspring presently i)rove. For the first 

 time we thus begin to get a rationale of "reversion." 



