On cyclical alterations in the Feulgen staining of nuclei during the development of nematodes

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Abstract
In the Ascaroidea the germinal vesicle, the pronuclei and the nuclei of all the blastomeres prior to chromatin diminution are strongly Feulgen positive. The nuclei of the somatic cells, which become suddenly Feulgen negative upon chromatin diminution, gradually become strongly Feulgen positive again during subsequent development. The nuclei of the germ track cells which are not subjected to chromatin diminution remain strongly Feulgen positive during the whole development. In all the other metazoa, including the nematodes where chromatin diminution does not occur, the germinal vesicle, the synkaryon and the nuclei of the blastomeres during the earliest cleavage stages are Feulgen negative. The latter, however, become gradually strongly Feulgen positive again during the subsequent development. The nuclei of the female germ cells and the synkaryon of protozoa and plants have also been reported to be Feulgen negative. Thus, the Feulgen-positive nuclei of the definitive somatic cells always originate from Feulgen-negative nuclei, in the Ascaroidea from the Feulgen-negative nuclei of the blastomeres and in all other forms of life from the Feulgen-negative nuclei of the eggs. The Feulgen-positive nuclei of the germ cells also originate from Feulgen-negative nuclei except in the Ascaroidea, where they originate from Feulgen-positive nuclei. In the somatic track the sequence of Feulgen-positive nuclei is interrupted in all forms of life and during the germ track it is also interrupted in all forms of life except the Ascaroidea, where it is uninterrupted. These biologically important phenomena are discussed. These investigations have been supported by a grant from the Knut and Alice Wallenberg stiftelse. The author is indebted to Mrs. M. Wahlström and E. Nowak for their valuable technical assistance.