Teratocarcinogenesis as related to the age of embryos grafted under the kidney capsule. 
Mouse egg-cylinders of C3H/H strain with two and three germ layers were transplanted under the kidney capsule.  They developed into well differentiated teratomas and teratocarcinomas.  Older embryos developed invariably into teratomas composed of adult tissues only.  We consider the period of germ layer inversion as a critical stage when embryonic cells loose their potentiality for uncontrolled growth.