[Crystals in the epithelial nuclei of the midgut of fleas].

On studying the changes in the epithelium of the midgut of Ceratophyllus tesquorum, C. laeviceps and Leptopsylla segnis intranuclear crystals were found during the process of digestion. They were recorded both from young and adult insects. The crystals were absent from nuclei of cells of regeneration nests, epithelium of the fore-intestine, any other organs or from nuclei of epithelial cells of the stomach of young non-feeding individuals. They were found neither in young nor in adult individuals of Xenopsylla conformis and Neopsylla setosa.