Two cell lines were derived from primary cultures of embryonic tissue of the tobacco hornworm, Manduca sexta (L.). The cell lines were maintained on hemolymph-free synthetic insect medium. Cytogenetic and immunoligical identification of the lines were carried out. Techniques for obtaining the line and medium, subculturieng and freezing procedures for long-term storage, and the morphological and growth characteristics are described.

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Apholate was injected into Melanoplus differentialis males, and periodically the meiotic chromosomes were microscopically examined during the subsequent 3-week period. The frequency of chromosomal aberrations was found to be highest among meiotic chromosomes that had been treated just prior to prophase I or during early prophase I. As prophase I progressed the resistance of chromosomes to breakage increased. Damage to chromosomes in the spermatogonia persisted and was observed in the spermatocytes.