254 Studies in the PhiisioUxjij of Fertilization 



(4) There is no ui)iJbriiiit,y in the fertilization percentages of eggs 

 from different parts of an oviduct, fertilized with equal amounts of a 

 given sperm-suspension. Sometimes eggs from the outer end, at others 

 eggs from the inner end are more readily self-fertilizable. Nor is there 

 any correspondence between the relative ease of self-fertilization and 

 that of cross-fertilization of eggs from different parts of the duct. 

 Pnjbably the same applies to sperm t;iken from different regions of the 

 vas deferens. Thus the degree to which eggs of a given individual can 

 be self-fertilized varies with each batch produced. 



(5) Contact with a suspen.sion of "own" spca-ni decreases the ease 

 with which eggs can subsequently be cross-fertilized. 



(()) The rates of segmentation of eggs cross-fertilized at increasing 

 lengths of time after the eggs and sperm have been brought into sea- 

 water either increase or decrease. 



(7) Cross-fertilized eggs from different regions of the oviduct seg- 

 ment at the same rates. This is also true for eggs cross-fertilized by 

 sperm from different parts of a vas deferens. 



(8) The rates of segmentation are independent of the percentages 

 of eggs self- or cross-fertilized. 



(9) The early segmentation lute is not slower in self- than in cross- 

 fertilized eggs, but the former hatch out a little later. Many of the 

 larvae from the self-fertilizations fail to settle down, and those which do 

 almost always die off in the course of a few days. 



(10) There is little or no relation between the relative rapidities of 

 segmentation and the stdisequent developnu'nt of different lots of cross- 

 fertilized eggs. In a given cultuiv, however, the larvae which .settle 

 down last develop worst. 



VII. Conclusion. 



In comparing Castle's and Morgan's work with the present results, 

 it is evident that there are races of Ciona intestinaUs which differ con- 

 siderably with reganl to their capacity for self-fertilization. This is not 

 exactly the same phenomenon as that originally discoveivd by Darwin 

 in Reseda and recently reinvestigated from a hereditary standpoint by 

 Compton (2). Here there are individuals which are completely self- 

 sterile and others which are completely self-fertile. Compton's work is 

 not as yet finished, but the results so fir obtaiiii'd indicate that in 



