ABSTRACT
In the case of a many-celled germ, however, where the cells are more or less alike, it is impossible to follow exactly the kinematics of early development without the help of experiment. The method of doing this which has been most successful consists in local intra-vitam staining, which at the same time forms the most useful means of studying the presumptive organ-regions. By the process of cleavage the germ is transformed from the unicellular to the multicellular state. The embryonic cells which thus arise may appear to be almost identical or may shew from the outset obvious and sometimes quite considerable differences. The fundamental processes of development must be taken to be essentially the same for all groups of animals; it is the outward form only that can vary according to the initial constitution of the germ.
