. Carnegie Institution of Washington publication. The Germinal Spot in Echinoderm Eggs. the question of the individuality of the chromosomes, nothing definite can be adduced. The process of chromosome formation here seems to be unique among echinoderms. The only similar case known to me is that described by Wilson in some of the sets of sea-urchin eggs stimulated to develop partheno- genetically by MgQ2, and here the chromatin nucleolus first resolved itself into a chromatic reticulum which subsequently broke up into chromosomes. OPHIOCOMA PUM1LA. The eggs of this brittle-star are of moderate
. Carnegie Institution of Washington publication. The Germinal Spot in Echinoderm Eggs. the question of the individuality of the chromosomes, nothing definite can be adduced. The process of chromosome formation here seems to be unique among echinoderms. The only similar case known to me is that described by Wilson in some of the sets of sea-urchin eggs stimulated to develop partheno- genetically by MgQ2, and here the chromatin nucleolus first resolved itself into a chromatic reticulum which subsequently broke up into chromosomes. OPHIOCOMA PUM1LA. The eggs of this brittle-star are of moderate size, being about that of Astcrias forbesii. Figure n shows an egg near the culmination of the growth-period. Maturation is probably imminent, for the nucleus has moved near the periphery and the nuclear wall is much shriveled. This assumption is confirmed by the fact that male individuals of this same col- lection carried sperm in ripe condition and very active. The cytoplasm is of the reticular type, with many microsomes and innumerable large dark- staining yolk-spherules. The nucleus has a homogeneous or very finely granular structure and remains unstained in basic dyes. Eosin reveals a delicate network. Scattered through the achromatic nucleoplasm are irregu-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Carnegie Institution of Washington. Washington, Carnegie Institution of Washington
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