322 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



fertilization may approach auto-fertilization. Thus a homozygous constitution 

 may be nearly attained in both the germ cells as well as in the somatic cells 

 of the adult forms, in constrast to the heterozygous condition which char- 

 acterizes, as a general rule, individuals belonging to the same species but to 

 different families or lines, which are not closely related to one another in their 

 genetic constitution and whose germ cells unite in the process of homoio- 

 fertilization. As the outcome of continued inbreeding, individual differences 

 are more and more lost. 



As stated, the individuals of higher species of animals are, usually, in 

 accordance with accepted terminology, heterozygous as far as their genetic 

 constitution is concerned. However, in order to indicate the relationship which 

 exists between the different types of fertilization, on the one hand, and of 

 transplantation and organismal differentials, on the other, it might be ad- 

 vantageous to designate as homoiozygosis the normal condition resulting 

 from homoio-fertilization, which, as we have seen, corresponds to a homoio- 

 transplantation. As a consequence of close inbreeding the normal homoio- 

 zygosis passes, then, into a state which might be designated as syngenesio- 

 zygosis, until at last a condition is approached corresponding to autozygosis, 

 but generally designated as homozygosis. By adopting the term "autozygosis", 

 we would express the genetic relationship to one another of the gene sets 

 which have been brought together in the fertilized ovum and in the individual 

 developing therefrom, in cases in which self-fertilization is the normal 

 process, or a genetic relationship which may be approached in cases in which 

 long-continued close inbreeding through many generations has preceded the 

 mating of the germ cells. Heterozygosis, in the sense in which this term is 

 used by geneticists, would then correspond to homoiozygosis, and the homo- 

 zygous condition of the geneticist would correspond to autozygosis, in the 

 sense in which the corresponding terms would be applied in transplantation. 

 In the genetic analysis of the effects of inbreeding and of transplantation, 

 we have to deal with closely related problems ; but this relationship is some- 

 what obscured by the terminology used, and, in particular, by attributing to 

 the terms "hetero" and "homoio" different meanings in the case of fertiliza- 

 tion and transplantation. The term "heterozygosis", as it is used in breeding, 

 is really meant to designate a dissimilarity in the gene sets of the different 

 individuals which are mated. In order to accentuate the mutual strangeness 

 of the gene sets or genes combined in zygotes, this condition might be desig- 

 nated as "allozygous", in contrast to the "isozygous" condition, which would 

 correspond to the homozygous state in the ordinary meaning of this term. 



In our discussion of transplantation we have analyzed the effects of close 

 inbreeding on the fate of the graft. It may therefore be of interest to com- 

 pare with the latter, the effects of close inbreeding on the character of the 

 offspring. It has been observed that in many instances the individuals of the 

 first generation, F lf derived from two parents possessing genetic constitutions 

 differing within a certain range, show an increase in size, fertility and, 

 strength, as compared with the parents, but in continuing the breeding of 



