Fig. I (Russell). Implant of embryonic end of divided 7-day mouse 

 conceptus beneath kidney capsule. Both donor tissue and reci- 

 pient animal were (CBAx A) F^ hybrid. This specimen was 

 removed 1 1 days after implantation and shows considerable pro- 

 liferation and differentiation ot embryonic tissues without appre- 

 ciable leucocyte response by the host. (Haematoxylin and 

 cosin. X 42.) 



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Fig. 2 (Russell). Implant of embryonic end ot divided 7-day 

 (CBAx A) Fj hybrid mouse conceptus beneath kidney capsule 

 of CBA mouse which had recently rejected two A-strain skin 

 grafts. The specimen was removed 10 days after implantation. It 

 shows complete destruction of the embryonic tissues of the implant 

 although in the upper left and lower right corners of the field 

 surviving trophoblastic giant cells can be seen. (Haematoxyhn 

 and eosin. x 70.) 



To face p. 134 



