A CRITICAL EXAMINATION 27 



"linkage" phenomena of inheritance. The diver- 

 gent Mendelian ratios obtained in such cases have 

 been variously explained. Bateson and Punnett 1 

 have advanced the theory of reduplication of 

 germ cells. This idea was first suggested in the 

 following terms : 



"The increase in number of the two types of 

 cell, AB and ab, may be reached by proliferation 

 of the two primordial cells of those two types. 

 It may further be remarked that though the 

 numbers characteristic of coupled systems cannot 

 be produced by simple dichotomies, they can 

 readily be represented as produced by a series of 

 periclinal and anticlinal divisions. For example, 

 if AB 1 by periclinal divisions give off AB 2 , and 

 this by anticlinal division become two cells, which 

 again divide periclinally and anticlinally, seven 

 cells AB are formed; by repetition of the same 

 processes 15 are formed, and so on." 



The direct cytological evidence in favor of the 

 reduplication hypotheses would seem to be ex- 

 tremely meager. The theory can, to be sure, 

 point to cytological observations which might 

 furnish a basis for the genetic results observed. 

 But this is a very different thing than a demon- 

 stration that they do furnish such a basis. 



1 The first statement of the reduplication hypothesis is found in 

 Bateson, W., and Punnett, R. C., "On the Interrelation of Genetic 

 Factors," Proc. Roy. Soc., B., Vol. 84, pp. 3-8, 1911. Further de- 

 velopments of the theory have been made by these authors, Trow, 

 Bailey, and others in recent papers in the Journal of Genetics. 



