No. GOU] 



525 



that they i)ro(liice grade off into effects that the ordinary 

 g-enes prodiiee. The chief intei-est in dcinon-t rat inu' (in- 

 stead of sjieciilating about) such ,<>-encs i> lh;it thcx uo far 

 towards helping us to a clearci' intci-iirctal i(»ti nf cci-tain 

 evidence that was heretofore ohscurc or Mrisiiilcrpri'tcd. 

 Wherever the history of the ori.uin of thi-c in- i^ 

 knowai it has ])een found to he the same as for other genes 

 and tlieir l)ehavior in Men<h'lian inheritance is precisely 

 the same. NevertheU'ss, Jennings has, in the ]iai)er al- 

 ready referred to, left certain ini])lications in regard to 

 thein that, if not clearly understood, may throw the sub- 

 ject into worse confusion tlian before. He seems to imply 

 — perhaps he does not really intend to do more— that 

 since through such modifying genes a perfectly contin- 

 uous series of modifications of a character may exist, 

 all real distinction becomes lost between contimious and 

 discontinuous variation. Xow as a matter of fact per- 

 fectly continuous characters, if due to ovei-lapi)ing of the 

 separate modifications, can he staiisi ic;ill\ handled, as 

 Johannsen has done for bean- and a- .lenninu- himself 

 has done for -ize di ftVM-ence^ in uarameriuni. ( Hher ways 

 are also knoun b\ uhieh tlie lorali/at ion in the .-In-nmo- 

 somes of Mio.lil\inu I'aetoi- mn b,. Mudied l.> mrthod- 

 that no student ol" M im<h'II,-ni heredity ran afford to n- 

 ject.^ All of this i^ familiar, of eour-'. to .lenniim-. lie 

 means, however, to sugiic^t that if the woi'k on f)n>s<ti>}iil(i 

 continues for anotliei- fifty xcars. >o many moditiers )H(Ii/ 

 be found that the ciiaracters will foi-m a continuous series. 

 Rut sux>pose the nmtants do become -o numerou- that it 

 is impossible to distinguish hetwi^t'ii ;m\ two l)y i!i>|uH'- 

 tion. Are we then to reject all ihc body of cvi^lcncc that 

 is fa^t accumulating that the modifyin- gcju- are ordi- 

 nar> Mcndrlian fact<.r^.' It wouhl be the height of ab- 

 sunlity to throw ovm-board all tlii- evperim.Mital ly (h-ter- 

 mined cNideiic' to the actual method <.f .uiiiin and 

 inheritan.-e of thcM- -.mh- li.'.'auM' ;i time mas cntm- u hen 



