QUANTITATIVE METHOD AND PRIMORDIA 37 



(Fi plants) the possibility D produces a reaction by which the 

 property D becomes observable. The property R is latent, 

 although the possibility R exists. In the offspring Fg of any 

 specimen whatever of F^ the possibility R awakens and the 

 property R becomes visible in 25 per cent, of the children. In 

 a similar way the transmission of the possibilities D and R 

 may be traced through the Fg, F4 . . . generations (although 

 the property R may be concealed in an unlimited lineage of 

 successive seed-bearers) because the possibility R is permanent 

 in the impure plants (true hybrids ; heterozygots) DR. 



REMARKS : (i) There is no difference in the observable 

 properties between the DD and the DR plants, although a 

 difference in the possibilities exists. 



(2) The appearance of the property R (which is only possible 

 in the RR plants) indicates the disappearance of the possibility 

 D. 



(3) The possibilities D and R may exist simultaneously (they 

 are not incompatible) although the properties D and R are 

 exclusive of each other. 



The facts alluded to in the present paragraph are inconsist- 

 ent with the notion that transitory or transitional forms (con- 

 tinuity) exist between the crossed species. 



§ 35.— MENDELISM. THE NOTION OF SPECIES {con- 

 tinued). EXCEPTIONS WITH REGARD TO THE PRO- 

 PERTIES. — In certain cases an intermediate property between 

 the properties D and R is observed in the offspring F^ of a 

 cross. 



EXAMPLE : In Hyoscyamus niger subsp. annuus (this is 

 the ordinary form) the corolla is brown. In H. niger subsp. 

 pallidus it is pale (the brown colour does not exist) . The cross 

 gives Fj plants with flowers of an intermediate tint, almost 

 exactly as if one part of the brown colour of annuus had 

 been diluted by addition of one part of the pale colour of 

 pallidus.^ 



BATESON has given a very interesting discussion of this 

 subject (intermediates and exceptions, loc. cit., pp. 235-244 and 

 245-265). He divides the examples of intermediate properties 

 and other exceptions on the rules laid down by MENDEL into 

 several classes. On the whole, we may conclude from the facts 

 mentioned by BATESON that in many examples it is possible 

 to prove that a so-called intermediate form exists only with 

 regard to a pair of observable properties, while the possibilities 

 are distinct and transmitted according to the principle of 

 segregation. 



» CORRENS. " Ueberdie dominierenden Merkmale der Bastarde." Ber. deut. 

 bot. Gesellsch. (1903), xxi., p. 133. Quoted according to BATESON, loc. cit. 



