Material and Methods

Abstract

Chick (Callus domesticus) embryos were used in this investigation. The eggs were incubated at 38° C. The embryos were as a rule fixed in Carnoy solution and graded according to the stages of Hamburger and Hamilton (1951). The stage number is placed as a suffix after HH⁻. After dehydration in alcohol and embedding in paraffin serial sections were prepared in the three conventional planes at 10–20 μ. The sections were stained with iron-hematoxylin or hematoxyline-eosine. A few embryos were fixed for control in 10% formalin or Bouin’s solution. Graphical reconstructions and wax models were made of the neural tube at the different developmental stages. The embryos used for reconstructions were coembedded with one to three sharp-edged slices of tissue (c′, c″, c‴, Fig. 1) which were placed vertically (Fig. 1a) to the plane of sectioning (d—d, Fig. 1a).