Submicroscopic Organization of the Nucleus during Spermiogenesis in the Grasshopper

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Abstract
The changes in the structure of the nucleus during spermio-genesis were investigated in ultra-thin sections with the electron microscope in 3 grasshoppers (Chortophaga viridifasciata, Chorthippus curtipennis and Romalea mlcroptera). The early spermatld nucleus, like other interphase nuclei, consists of a mass of much twisted fibrils 200 A thick. Each of these fibrils is made up of 2 thinner ones, about 100 A thick. As the nucleus elongates the fibrils straighten out and become more or less oriented in the long axis of the nucleus. Each 100-A fibril then splits into 2 fibrils about 40 A thick. These 40-A fibrils line up side by side to form sheets or membranes which are folded randomly in the nuclear space. Cytochemical tests show that this sheet formation occurs at the time when the non-histone protein disappears. As the nucleus further elongates the membranes become packed together to form a regular honey comb pattern. The spaces between the membranes then are gradually obliterated until the nucleus becomes a homogeneous mass.