[Regeneration, differentiation and moulting hormones in the cockroach embryo cultured in vitro].

1. The second moulting cycle of the cockroach embryo may be divided into 2 parts: during the first one, regeneration of appendages is possible in embryos cultured in vitro; it is not possible during the second part. 2. Regeneration takes place inside the cuticle of the stump in 4 phases: 1) epidermal wound healing; 2) morphallaxis; 3) growth by cell proliferation; 4) secretion of the cuticle. 3. The regenerative capacity does not seem to depend on hormonal secretions and is apparently an intrinsic property of the epidermal cells of the appendages. 4. The addition of exogenous moulting hormone to the culture medium inhibits the regeneration and causes precocious formation of spines and hairs and secretion of the cuticle. 5. A relatively short period of contact (24 to 30 h) with the hormone triggers a chain of processes which then continue in its absence (formation of spines and hairs, secretion of the epicuticle and then of the procuticle). 6. There is an incompatibility between regeneration and differentiation, as if these two functions corresponded to two progammes, one of which is inhibited and the other triggered by a high concentration of hormone. 7. The moulting hormone is not produced exclusively by the prothoracic glands.