stout: pollinations in CICHORIUM INTYBUS 349 



the same individual by the use of ether, by changing temperature, 

 or by using various chemicals specially influential in altering 

 surface tension of the eggs. Experiments to determine if such 

 incompatibility could be acquired through transplantation were 

 likewise negative. It was found that body fluids inhibit all 

 fertilization evidently from causes quite different from those 

 operating in self-incompatibility. 



In the artificial removal of eggs and sperm for these experiments, 

 the difhculty of securing good sperm was a source of much experi- 

 mental error, but Morgan's results show that self-sterility was the 

 rule and that only to a limited degree does self-fertilization occur 

 in his strains, while general cross-fertility is nearly always possible 

 provided both eggs and sperm are in good condition. 



Morgan considers that this self-incompatibility is due to an 

 absence of the necessary reaction between egg and sperm as the point 

 of contact and that such inaction is because of similarity. Con- 

 versely, the entrance of sperm into the egg in cross-fertilization 

 is due to the necessary reaction occurring as a result of differences 

 between the egg and sperm. Morgan very adequately points 

 out that self-sterility of this sort is not due to a similarity of 

 "hereditary factors" carried by the sex cells, for they are haploid, 

 and are derived from parents that cannot be considered homo- 

 zygous. They can only be considered similar because both have 

 developed in the same individual. They are alike, he points out, 

 only because their protoplasmic substances have been under the 

 same influence. 



It should be noted that Morgan points out that -such a con- 

 dition might also arise from inbreeding in which what is called 

 "homozygosity" might develop, giving similarity to the hereditary 

 complex. In 1904 Morgan suggested that although in all self- 

 fertilized hermaphrodite, animals and plants the common origin 

 of the sex organs involves conditions identical with those assumed 

 to cause self-sterility in Ciona, the action may be less marked 

 and not sufficiently strong to give self-sterility. 



This analysis of the generalized term "constitutional similarity" 

 assumes that in self-sterile strains of plants and animals, in which 

 crossing is necessary for reproduction, the similarity must be 

 conceived to rest in individual cytoplasmic relations. This is the 

 conclusion that Morgan makes as late as 19 13 in a general review 



