CHANGING NUCLEAR HISTONE PATTERNS DURING DEVELOPMENT I. FERTILIZATION AND EARLY CLEAVAGE IN THE CRAB, EMERITA ANALOGA

Application of cytochemical techniques to the early developmental stages of the decapod crab, Emerita analoga, shows the following. After fertilization, the sperm nucleus, which apparently contains no basic proteins prior to this stage, becomes associated with a class of weakly basic histones, which differ from adult type histones in their apparent inability to bind alkaline fast green and from protamines by their inability to bind bromphenol blue following acetylation. This class of histones only persists until the late pronucleus stage, by which time the chromosomes contain a class of histones that are indistinguishable from adult histones by qualitative cytochemical techniques. No further changes in the nuclear histones are detected in the zygote or early cleavage stages. These changing histone patterns during early crab development are discussed with reference to other similar studies in other organisms.