Chapter J 



The Role of Organismal Differentials 

 in Fertilization 



In preceding chapters we have considered the joining together of proto- 

 zoa, ova, blastomeres, amoebocytes, and more differentiated tissue cells, 

 in their relation to organismal differentials, and we found that in general 

 agglutination processes play a significant part under these various conditions. 

 A somewhat similar process takes place when two cells unite in the fertiliza- 

 tion of an ovum by a spermatozoon, although the interaction between these 

 two cells is of a more complicated nature. 



It was O. Hertwig who first drew attention to the similarity which exists 

 between the process of fertilization and transplantation, fertilization being 

 considered as the transplantation of a spermatozoon into an ovum. He desig- 

 nated the relationship between these cells, upon which their mutual com- 

 patibility depends and which may vary in different combinations, as sexual 

 affinity, and distinguished it from the vegetative affinity which determines 

 the relationship between somatic transplants and hosts. Later, W. Schultz, 

 who, within a limited range, carried out investigations concerning the rela- 

 tionship between transplantability and genetic conditions, tested experimen- 

 tally the question as to whether a parallelism exists between transplantability 

 of parts of heterogenous individuals and the feasibility of hybridization be- 

 tween the same host and donor species. 



However, although in certain respects transplantation and fertilization are 

 analogous processes, there are also some essential differences which had not 

 yet been clearly recognized by Hertwig. While in both processes the result 

 depends upon the relationship between two organisms or parts of organisms, 

 the kind of genetic relationship which is normal or optimal is not the same in 

 both cases. Whereas the relationship between spermatozoon and egg is usually 

 homoiogenous, and this is the one best suited for a successful fertilization, 

 such is not the case in transplantation of adult tissues in higher organisms. 

 Here a homoiogenous relationship between the organismal differentials of 

 host and graft leads, as a rule, to severe reactions and to injury of the trans- 

 plant. Furthermore, in transplantation of differentiated tissues in higher 

 adult hosts we have to deal with the interaction of two fully developed 

 organismal differentials, whereas in fertilization we have to deal, in the main, 

 with the transplantation of nuclear material, and especially of the chromo- 

 somes of the spermatozoon, into a cell which likewise does not yet possess a 

 fully developed organismal differential, nor the mechanism by means of 

 which differentiated organisms react against strange organismal differentials. 

 Ovum and spermatozoon each carry a substance or substances which later in 

 the course of embryonal development will give origin to a fully formed 



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