92 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



ent litters of inbred families. In 10 transplantations, brothers or sisters which 

 were hybrids between two individuals from families 32, 39, 35, 13 or 2 were 

 used. In six of these transplantations one of the parents belonged to family 13, 

 while the other parent belonged to families 32, 35 or 2. The grades were 3—, 

 3 — , 3 + , 3, 3, 3/3 — . In the remaining four transplantations, the parents that 

 entered into the hybrid composition belonged to families 39, 2, 32, or 35 ; the 

 grades were 3, 3 + , 3+, 3. In these two sets of transplantations, the average 

 grades were 2.94 and 3.12, respectively. While the difference between these 

 two averages is perhaps too small to be of much significance, both these grades 

 are slightly less favorable than those obtained in brother-to-brother trans- 

 plantations in the closely inbred strains. This is presumably due to the fact 

 that in hybrids a summation of the effects of strange genes takes place, which 

 latter may still be found in some individuals in inbred strains. 



D. As controls, transplantations were carried out between brothers in non- 

 inbred stock. In former experiments of this kind, the average grade was 2/2— 

 (1.87). In 15 additional experiments in stock B guinea pigs, the average grade 

 was 1.91. These grades are better than those obtained in transplantations be- 

 tween non-related, non-inbred guinea pigs, in which the average grades were 

 1.27 and 1.11, but they are much lower than the average grades obtained in 

 transplantations between brothers in inbred strains. 



E. Transplantation front a hybrid between two inbred families to one of 

 the parent families. 25 experiments were made; in each case an F x hybrid 

 was used as the donor. In no case was one of the actual parents used as host, 

 but merely the families to which the parents belonged. Examination took place 

 between 21 and 37 days after transplantation. The average grade was 1.75, 

 which corresponds to a severe syngenesio-reaction, but is somewhat higher 

 than the average grade found in homoiogenous transplantations. Here, again, 

 it appeared that the severity of the reaction was strongest in transplantations 

 in which family 13 was a component part of the donor, even if the host be- 

 longed not to family 13, but to the other parent family which entered into the 

 hybrid. There were six transplantations in which family 13 entered as a parent 

 strain in the donor; in three of these, strain 13 was likewise the host. The 

 other parent family was 2. The grades in these six transplantations were as 

 follows: 1.25, 1, 1.12, 1.25, 1, 1.25. The average grade was 1.14, which cor- 

 responds to a severe homoiogenous reaction. There were 13 transplantations 

 in which family 32 entered into the hybrids, and in six of these it was also 

 host. The grades were as follows: 2.12, 2, 1.87, 1.87, 2, 2, 3.25, 1.87, 3, 1.12, 3, 

 1.87, 2.75, corresponding to an average grade of 1.98. The average grade of the 

 experiments in which strain 32 was also host was 2.5. The other component 

 families were 2, 35 and 39. There remain six transplantations in which families 

 2, 35 and 39 entered ; here the average grade was 1.65. There are, then, at least 

 strong indications that the presence of family 13 in the hybrid intensified the 

 reaction against the graft and that the presence of family 32 in the donor, and 

 especially also in the host, mitigated the severity of the reaction. It is not 

 probable that the strong reaction against family 13 is due actually to a lesser 

 effect of the long-continued inbreeding, but to a greater reactivity of family 



