Metachromasia Observed in the Living Eggs of<i>Arbacia punctulata</i>and its Cytochemical Analysis

Abstract

ABSTRACT The analysis of the egg of Arbacia punctulata by means of vital staining with toluidine blue confirms the results obtained on other species. It shows a primary metachromasia due to tiny a granules scattered throughout the cytoplasm, and the appearance, at the time of the paired pronuclei, of secondary metachromatic β granules in close relation to the nucleo-mitotic apparatus. High-speed pressure-centrifugation (Marsland’s procedure) shows that the a granules are sedimented in the upper half of the vitelline zone, the ft granules in the lower half of the hyaline zone. These two metachromatic layers remain separated by the mitochondrial band. A third granular, metachromatic material can be detected which may be a precursor of the βgranules. Cytochemical tests verify the presence of acid phosphatase in all the metachromatic structures and show that all contain mucopolysaccharides, which account for the metachromasia. The Alcian-blue technique reveals that the β granules contain strongly acidic mucopolysaccharides, whereas the a granules contain less acidic mucopolysaccharides.