Ultrastructure of cell division in insect spermatogenesis

An electron microscopic examination has been made of the testis of the cockroach after fixation with glutaraldehyde. The tubular components of the spindle of cells in the first meiotic division consist of chromosomal tubules, continuous tubules, and interzonal tubules. Chromosomal tubules run between the centrosphere and the kinetochore, but they are sometimes seen passing into the substance of the chromosome. Continuous tubules are seen at metaphase, passing from pole to pole through gaps between the chromosomes at the metaphase plate. Interzonal tubules are found at anaphase, extending between the tapered equatorial ends of the chromosome bivalents. Their presence is apparently characteristic of meiosis, for we have not seen them previously in somatic mitosis. Electron dense material of an unknown nature appears in the plane of the equator in association with continuous tubules at metaphase and interzonal tubules at anaphase.