SELF-FERTILIZATION INDUCED BY ARTIFICIAL 



MEANS. 



BY 



T. H. Morgan. 



It has long been known that the pollen of some plants will 

 not fertilize the ovules of the same plant. The cause of this 

 impotence has not yet been detected. 



It is also known that pollen from another plant is often pre- 

 potent in those cases where normal self-fertilization may occur. 

 It has further been shown, especially by Darwin, that the offspring 

 from self-fertilized ovules are in general not so vigorous as those 

 from cross-fertilized ones. 



There are here two problems, which, even if they should prove 

 to be fundamentally related, can be most profitably examined 

 separately; — first, the problem of the Inability of the male ele- 

 ment to fertilize the female germ-cells of the same individual; 

 and, second, the effect of self-fertilization (in those cases In which 

 It occurs) on the offspring. Both problems appear to be within 

 the range of experimental examination. 



There are only a very few cases known amongst animals where 

 conditions similar to those in plants have been found to prevail, 

 although very few hermaphroditic animals appear to have been ex- 

 amined in this respect. Close inbreeding, which is commonly sup- 

 posed to bring about deterioration in some cases. Is perhaps not 

 very dissimilar to self-fertilization. Whether in the case of in- 

 breeding there is ultimately a loss of power to fertilize the egg, 

 or whether the egg fails to develop after It has been fertilized, 

 has not, so far as I know, been determined. 



Castle discovered in the ascidian, Ciona intestinaUs, a case ap- 

 parently similar to those in plants. The eggs are generally In- 

 capable of self-fertilization, yet can be readily cross-fertilized; i.e., 



