QUANTITATIVE METHOD AND PRIMORDIA 39 



has been produced.^ This subspecies is strictly distinct from 

 its parents by the seed-fixed possibility H even if the corre- 

 sponding property H were variable, inclining (goneochnous) 

 sometimes toward one of the parents or towards the other, 

 according to the principle of plasticity. (Compare the variable 

 colour of the peas, p. 38.) 



We might be tempted to call the new subspecies H an inter- 

 mediate between the parents. The term intermediate implies, 

 at least in biological language, the idea of transition, gradual 

 passage, continuity. Since the subspecies H is strictly distinct 

 from both parental species (in spite of the possible variability 

 of the property H), it is not a transitory form. Therefore I 

 think it is preferable to call it an interposed subspecies. (See 

 § 105.) 



The difference between transitory and interposed may be easily realized by 

 means of a comparison. The two parental species may be compared to two 

 terms a and c of a chemical series, for instance — the acrylic series (§ 5 ), in which 

 the atoms of carbon are n and n + 2 in number. Between the chemical species 

 a and c certain differences e^ist in the observable properties — for instance, in 

 the temperature of fusion. The subspecies H is comparable to the term b 

 in which the number of atoms of carbon is n + i. The term b is separated 

 from a and c by two distinct gaps with regard to the constitution of its mole- 

 cule and also by its melting -point. ^ There is no continuity between a, b and c. 

 The term b is not transitory, but interposed between a and b. 



The number of facts which are ruled by the principle of 

 segregation is very large, and the examples which at first sight 

 seemed to be exceptions, but were later on proved to follow the 

 Mendelian rule, are already numerous. Even if exceptions 

 really exist, it is impossible not to accept the principle of 

 segregation in point of fact as a biological rule. 



Perhaps we may again have recourse to a comparison. Every 

 biologist accepts as a rule the proposition that the develop- 

 ment of a female germ is impossible without fertiUzation, 

 although numerous examples of parthenogenesis are known. 



It is also accepted as a rule that flower-visiting insects (bees, 

 etc.) play an important part in the fertilization of flowers. 

 The number of species which are partially or completely sterile 

 when deprived of the aid of insects is so large that any doubt 

 about the reality of the mentioned rule is excluded, although 

 many examples of self-fertile plants are known, and although 

 in a number of flowers which are visited by crowds of insects 

 attracted by honey and perfumes seeds are produced by 

 apogamy. 



* This conclusion was adopted by JANCZEWSKI with reference to the 

 hybrid Anemone silvestris x magellanica . (Bateson, loc. cit., pp. 250-251.) 



If this suggestion were proved to be exact we would find in hybridization 

 one of the possible causes of mutation. (In § 9 another possible cause is men- 

 tioned. See also § 105.) 



* Although this temperature is variable according to external influences, 

 such as pressure, for instance. 



