[Localization of cholinesterase-Activity during gastrulation of the sea urchin embryo].

The localization of cholinesterase (ChE)-activity during gastrulation of the sea urchin embryo was investigated at the cellular level by histochemical methods.ChE-activity was found in primary and secondary mesenchyme cells and in the invaginating archenteron.In the course of development, ChE-activity disappears from primary mesenchyme cells.

[The induction of visceral cartilage from cranial neural crest by pharyngeal endoderm in hanging drop cultures and the locomotory behaviour of the neural crest cells during cartilage differentiation].

1. Cranial neural crest cells and pharyngeal primordia ofTriturus alpestris were cultured together by the hanging drop method at 20 °C. 2.

[The inducing capability of nucleic acids tested on amphibian ectoderm].

Ribonucleic acids were extracted from chick- andTriturus embryos by the phenol method and tested for their inducing ability:Ribonucleic acids from chick embryos had only a weak inducing capacity compared with that exerted by inducing chick embryo protein fractions. In tissue cultures of undetermined amphibian ectoderm they induced unspecific neural structures, mesenchymal cells and melanophores only to a small extent. But the differentiated part of the tissue was still higher than in control series where the ectoderm was cultivated in Flickinger solution alone.