Vol. XXXVIII. May, 1920. No. 5. 



BIOLOGICAL BULLETIN 



SELECTIVE FERTILIZATION IN POLLEN MIXTURES. 



D. F. JONES, 

 CONNECTICUT AGRICULTURAL EXPERIMENT STATION, NEW HAVEN. 



Equality in fertilizing power of gametes dissimilar in the 

 hereditary factors they carry is a corollary of Mendelism. It 

 has been thought that certain exceptions to this general rule 

 may exist. Differential fecundating ability has been suggested 

 from time to time as a possible interpretation of otherwise un- 

 accountable results. The earlier uses of this hypothesis of 

 inequality in sperm efficiency, such as Castle's (1903) theory of 

 sex determination, Cuenot's (1908) conception of the reason for 

 the non-appearance of homozygous yellow mice, have since been 

 found to be unnecessary. The interpretation of linkage phe- 

 nomena according to the reduplication hypothesis, while essen- 

 tially different in application, holds somewhat the same implica- 

 tion as selective fertilization, that is, differential operative power 

 of cells of unlike germinal construction. 



As the yellow mouse problem was finally resolved to a selective 

 elimination of zygotes so many puzzles have had considerable 

 light thrown on them by a more complete understanding of the 

 factor relations. Many instances of the non-appearance of cer- 

 tain types are known to be the result of the action of lethal factors. 

 Good illustrations of/ this are found in Drosophila (Muller, 1918). 

 Other cases of elimination immediately after fertilization or early 

 in development are known in maize. 



Sometimes abortion of a part of the gametes before fertilization 

 takes place and it is assumed that the elimination is selective. 

 Belling (1914) has shown that in Stizolobium 50 per cent, of the 

 pollen grains and ovules regularly abort in certain types. The 

 aberrant results from the (Enotheras are now generally considered 

 largely, if not wholly, to be due to differential destruction of both 



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