A correct interpretation of gastrulation is impossible without a knowledge of the position which the presumptive germinal layers occupy in the blastula. This position may be ascertained in various ways. A chart, showing the fate of each part of an early embryo, in particular, a blastula, is called a fate map. In tracing the fate of various parts of the [...]
In this article we will discuss about the selective affinities of cells as a determining factor in cellular rearrangements of an embryo. We may ask what is the nature of the forces which control the rearrangement of cells resulting from morphogenetic movements in gastrulation and also in other morphogenetic processes; we may ask whether the new positions of the cells [...]
In this article we will discuss about the gene activity during gastrulation period of embryos. Fragments of sea urchin eggs not containing the nucleus may be treated with agents who cause parthenogenetic activation of the egg (viz., hypertonic seawater). It has been found that the non-nucleated fragments begin to cleave and may reach the morula stage. The animals (embryos), however, [...]