Induction of lens tissue by lens epithelium in frog embryonic ectoderm

The inductive influence of differentiated lens epithelium on embryonic ectoderm taken from gastrula and neurula stages ofRana temporaria frogs has been studied using tissue cultures. The following results have been obtained: 1. Induction of lentoids takes place when there is direct contact between lens epithelium and embryonic ectoderm. 2. When cultivated in contact with basement membrane of lens epithelium, ectoderm develops into typical epidermis. 3. Lens fibres do not produce lens induction. 4. Lens epithelium treated with 96° ethanol does not induce lens tissue, and it does not acquire new inductive properties as a result of the treatment. 5. Lentoids that have been induced by living lens epithelium display a positive immunofluorescent reaction. The results obtained suggest that in the phase preceding terminal differentiation, cells of the lens epithelium contain a lens-inducing substance. The possible role of this substance in the chain of events leading to lens formation in development is discussed.