Chapter £ 



Self Fertilization and Autogenous 

 Transplantation 



In the preceding chapter we have compared the effects of heterogenous 

 and homoiogenous fertilization and transplantation. We shall now con- 

 sider the significance of self-fertilization, which, if continued through 

 successive generations, may lead in the end to a very great similarity or to iden- 

 tity in the genetic composition of spermatozoa and ova ; we shall also con- 

 sider the influence of close inbreeding, a process which may have a similar 

 effect as far as the genetic composition of egg and spermatozoa are con- 

 cerned. In order to indicate the analogy between these two processes and the 

 corresponding types of transplantation, self fertilization may be designated 

 as autogenous fertilization, because in this case the two germ cells have de- 

 veloped in the same individual, and fertilization between nearly related indi- 

 viduals may be designated as syngenesiofertilization. Close inbreeding im- 

 plies serial syngenesious fertilization, and through such brother-and-sister 

 matings a relationship may be attained between members of the inbred group, 

 which, while still in the syngenesious region of the spectrum of relationships, 

 may at last approach an autogenous condition. 



As we have seen, genetic factors largely determine the character of the 

 precursors of the organismal differentials in the embryo, as well as of the 

 fully developed organismal differentials, which latter control the interaction 

 between adult tissues; genetic factors play a part also in the interaction be- 

 tween egg and spermatozoon. In addition to these two kinds of interaction 

 there exists a third type, which, while not identical with these, possesses 

 some of the characteristics of both. This third type is represented in the 

 fertilization process in some higher plants. Here we have to deal neither 

 with the direct interaction of spermatozoon and egg, nor with that of two 

 different tissues, but with the interaction of a structure associated with or 

 containing the male germ cell, the pollen, with a specialized tissue which 

 surrounds the egg, and ultimately, with the egg itself. During this process, 

 mechanisms may be active which prevent self-fertilization, when both ovum 

 and spermatozoon originate in the same individual. In plants, incompatibility 

 between pollen-tube and tissues which surround the female sex cell may like- 

 wise prevent a successful fertilization if ovum and pollen belong to differ- 

 ent species or to different varieties. However, in the case of heterofertiliza- 

 tion the pollen-tube may, in some instances actually reach the eggule, but even 

 then a successful fertilization may be prevented, owing to incompatibilities 

 between nuclear or cytoplasmic constituents of the germ cells. We must then 

 consider the spectrum of compatibilities and incompatibilities under the fol- 

 lowing three conditions, (1) in the interaction of tissues after transplantation, 



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