ABSTRACT
This chapter describes some features of cell division that are important in understanding animal development and illustrates these features with details of cell division in the embryos that are most commonly used for research. Hans Driesch started his career as an embryologist and made fundamental contributions to the subject. Even the most famous experimental embryologist of all time, Hans Spemann, a contemporary of Driesch, was undecided about vitalism. Various methods of study are used, the simplest being to study whole embryos or sections of embryos under the microscope at various stages of development. Each embryo was put on gel on a microscope slide and covered with a glass coverslip. The cleavage plane again passes through the animal and vegetal poles but at right angles to the first to give rise to the upper and lower halves of the embryo. The fate of groups of cells of Xenopus embryos has been studied by staining.
