SELF FERTILIZATION 325 



limit, toxic effects would predominate and disharmonies would occur in the 

 process of fertilization or in the development of the embryos. If we accept 

 this mode of interpretation, we should have to assume that in homoiogenous 

 fertilization, which represents the normal process, the injurious effects of in- 

 breeding are avoided, because in the former case there is provided the stimu- 

 lation which slightly toxic substances exert on the developing ovum. We 

 would then have to deal with substances, the character of which depends 

 upon the relationship between the male and female germ cells, a certain 

 distance of relationship, but one not exceeding a definite limit, giving the best 

 results. 



Of interest in this connection are also the experiments of Demoll, who 

 found that the injurious results of inbreeding in mice can apparently be 

 neutralized by administration of small doses of arsenic to the breeding in- 

 dividuals. It seems, however, that in the deterioration caused by inbreeding 

 we have essentially to deal with genetic reactions and that arsenic, if it should 

 be potent at all, merely prevents some of the injurious results from becom- 

 ing manifest, without essentially changing the underlying causes of the 

 deterioration. Such a method would therefore represent merely a symptomatic 

 treatment, and with this interpretation agrees the fact mentioned by Demoll, 

 although not interpreted by him in this way, that following the cessation of 

 the arsenic administration the injurious consequences of inbreeding again 

 became manifest. 



Demoll furthermore attributed the favorable effect of homoiogenous com- 

 binations of sperm and egg to the formation of antibodies, the strange sper- 

 matozoon acting as an antigen in the egg and eliciting here, or in the develop- 

 ing embryo, the production of antibodies, which interact with the antigen. 

 However, the production of antibodies presupposes the presence of mecha- 

 nisms which, to our knowledge, form only during the later embryonal, or even 

 post-embryonal life. Within the same organism all the constituent normal 

 parts have, as far as their mutual relations are concerned, an autogenous 

 character and they are therefore not able to function as antigens. Thus it is 

 hardly conceivable that in mechanisms so well regulated as are those of 

 embryonal development, abnormal processes of a variable character, such 

 as the formation of antibodies, should play a role. 



We mention these physiological viewpoints, although the interpretation of 

 East and Jones, as to the mechanisms by means of which inbreeding exerts 

 its injurious effects, seems to have been generally accepted by geneticists. 

 However, genetic and physiological modes of interpretation are not neces- 

 sarily mutually exclusive. 



