322 Forms of Beduplieafion 



There seems to be no reason why the most various types of re- 

 duplication should not occur together in the same plant as the result of 

 the same cross. The hypothesis of reduplication seems adequate to 

 explain the occurrence of any type of ratio. 



The most suggestive point which emerges from the analysis is the 

 importance of the product nmp ... and of its constituent factors. From 

 these, when all the factors and all the ratios in any one cross have Ijeen 

 ascertained, it should be possible to compute the minimum number of 

 successive cell-divisions needed to produce the complete system of 

 segregation. It ought to be possible to determine also, in sweet-peas 

 for example, the number of successive cell-divisions which normally 

 intervene between the first division of the zygote and the last of the 

 gametogenic divisions, and the distribution of these in the ontogeny. 

 Comparison of the two results might serve to fix the stage at which 

 segregation takes place. 



It is then advisable to distinguish between primary and secondary 

 reduplications. A ratio of reduplication ascertained by experiment may 

 belong to either series. The gametic series is based upon the primary 

 reduplications alone. Every observed type of reduplication must be 

 assigned to its pi-oper position. It is comparatively easy, as we have 

 seen, to calculate the secondary from the primary reduplications. 



The schemes on p. 323 will illustrate the relationships of primary 

 and secondary reduplications. 



It is perhaps advisable to add that systems of segregation will 

 probably be seldom found in which all the primary reduplications take 

 place between one factor A and a number of others B, C, D, E, etc. 

 Primary reduplications may occur between any pair of factors, and the 

 consequent secondary reduplications will undergo corresponding modi- 

 fications. 



The construction of the gametic series, when the ratios of primary 

 reduplication are known, is easy, and from these any secondary re- 

 duplication is ascertainable. The following scheme illustrates such 

 a system of reduplications : — 



Primary 

 reduplications Secondary reduplications 



A and B = ?i : 1 



BandC = ;K:l AandC= nm + 1 : n + ?h 



C and D = p : 1 A and D = hhi/i + ii + iii+p: iim + np + mp + 1 B and D = iitp + 1 : 7n +p 



