168 Messrs Bateson and Punnett, A suggestion as to the nature, &c. 



organs in the lateral florets, and even absence of the lateral florets 

 altogether was found to be dominant over the presence of fully 

 developed flowers. Doubtless the statement could be inverted, 

 and it could be suggested that the absence of the florets, etc., was 

 due to the -presence of some element which prevented their growth, 

 but that would be to abandon all judgments based on the actual 

 appearances, and the terms would become meaningless. 



The next question is whether hypotheses of presence-and- 

 absence provide a substitute for the conception of compound 

 allelomorphs. In many cases it is likely that characters at first 

 sight reckoned as compound will prove to be made up, like the 

 walnut comb, by the co-existence in one zygote of elements 

 belonging to distinct allelomorphic pairs. 



For instance, the colour of a flower, made up of both sap- 

 elements and plastid-elements, might pass for a compound character. 

 Here a disproof is easily obtained from the fact that such a flower 

 when crossed with white will give in F 2 the four types, sap-colour 

 alone, sap-colour + plastid-colour, white alone, plastid-colour alone. 

 Conversely a red crossed with cream (viz. plastid-colour) will give 

 some whites in F 2 , as in Sweet-peas and Stocks*. But that there 

 are limits to the extension of this principle is suggested, e.g. by 

 the class of cases in which F 2 contains a number of new types, 

 though one of the original pure types may not reappear. Such a 

 case is that of Brown Leghorn x White Leghorn, which gives in 

 F 2 cuckoo, slaty, pile, etc., but the Brown Leghorn colour has not 

 reappeared in about 500 chicks. 



Other cases with which any hypothesis of the mere presence 

 and absence of characters cannot apparently deal are to be found 

 among the phenomena of reversion and the peculiarities seen in 

 the behaviour of extracted types ; but until the evidence on this 

 part of the subject is more complete it can scarcely be profitably 

 discussed. 



* Boy. Soc. Evol. Com. Rep., 1905, n., pp. 27 and 86. 



