[The building up and maintenance of steep temperature gradients in biological objects accessible to developmental observation and photomicrographic registration].

For causal analysis of morphogenetic systems a device has been developed (Fig. 1) which achieves a well-defined and stable temperature gradient up to 80° C/mm inside small objectsin vivo. The technique requires that the objects are embedded in aqueous agar of 3% (Difco, Detroit/Michigan). By means of an inverted microscope time-lapse cinematography of the objects can be carried out simultaneously.