THE TRANSMISSION OF INFORMATION DURING PRIMARY EMBRYONIC INDUCTION

SUMMARY This paper contains a discussion of some recent results obtained with respect to the transmission of inductive information and detectable material from the inductor to the responding ectoderm during primary induction. It may be concluded that the inductive stimulus is capable of operating over a certain distance without cytoplasmic contact. The mechanism of this transmission is unknown, but the findings from various experiments have shown that a transfer of materials from the inductor to the ectoderm does occur during the process of induction. The transmission of inductive information is time-dependent, and this is due, at least in part, to delayed release of the active compounds from the inductor tissue. On the other hand, the reactivity of the responding tissue changes with time, and the type of differentiation initiated by an inductive stimulus is dependent upon the time of its application. Thus different factors have always to be considered when the results obtained from such induction experiments are being interpreted: the amount and the quality of different active components, their release by the inductor tissue, and finally the selective changes in the competence of the responding ectodermal cells.