Enucleation of sea urchin eggs: II. Enucleation of animal or vegetal halves

Abstract

1. 1. Sea urchin blastomeres at the 8 cell stage were enucleated in such a way that either the 4 animal or the 4 vegetal cells were deprived of their nuclei. 2. 2. The enucleated cells usually formed asters and always divided irregularly, but they were never observed to differentiate or become incorporated into any larval organ or structure. 3. 3. Of the 37 animal halves with enucleated vegetal cytoplasm which developed into larvae, 36 revealed no vegetal influence as compared with the control animal halves. The interpretation of one larva was inconclusive. 4. 4. Of the 37 vegetal halves with enucleated animal cytoplasm, 8 revealed a marked animal influence, i.e. they formed more or less well developed plutei whereas the control vegetal halves never displayed a comparable degree of differentiation. 5. 5. Six of the 8 positive results with vegetal halves were obtained in 1950 and only 2 in 1951, although the number of experiments done in 1951 was 29 as compared with 8 in 1950. 6. 6. The tentative conclusion is that enucleated vegetal cytoplasm does not influence the differentiation of the animal half, but enucleated animal cytoplasm may influence the vegetal half.