166 



Scientific Proceedings (120). 



case of reciprocal transplants between Japanese waltzers and Fi 

 generation hybrids, formed by crossing together the waltzers and 

 the albinos. 



In this case, analogy with the tumor work and knowledge of 

 the genetic constitution of the animals lead us to suspect that 

 implants of waltzing mouse spleen should grow in the Fi hybrids, 

 while implants of splenic tissue from the hybrids should not persist 

 in the waltzing mice. This was actually found to be the case, as 

 can be seen from the two bottom lines of Table I. 



The gametes of the Japanese mice were, by hypothesis, essen- 

 tially equal in respect to their genetic factors. Each Fi hybrid 

 had therefore received from its waltzing mouse parent approxi- 

 mately the same genetic contribution. This was of such a nature 

 as to make possible the persistence of implants coming from the 

 Japanese mouse. (The same was found to hold true in the case 

 of tumors of the Japanese mouse.) 



The Fi tissue which was implanted in the Japanese waltzers 

 comes from animals approximately half of whose genetic consti- 

 tution is determined by their albino parent. Since the Japanese 

 mice had not the genetic factors which made up the albino complex, 

 we should not expect that they could support the hybrid implants. 



The results, therefore, in all three series are in complete 

 harmony with the hypothesis advanced by Little and Tyzzer 

 (1916), namely: that the susceptibility of any mouse to implants 

 of foreign tumor tissue depends upon the genetic constitution of 

 the host in its relation to the genetic constitution of the animal 

 from which the implant was taker. 



The value of the term " syngenesiotrans plantation" seems to be 

 greatly impaired for: 



(a) Parents (waltzers) failed uniformly to support implants of the 

 splenic tissue of their progeny. 



(b) Progeny (F x hybrids) grew regularly the splenic tissue of their 

 parents. 



There is in this case an absolute difference in the results obtained, 

 depending upon which race is used as the host. The fact that the 

 "genetic" relationship changes while the "pedigree" relationship 

 remains the same, shows that the former is the important factor in 

 determining the nature of the result. 



