Abstract
In the development of the flagellum of the Tenebrio sperm, a peripheral ring of nine accessory fibers appears as a result of outgrowths from the outermost side of each of the B subfibers. In the mature sperm, after lead staining, the accessory fibers appear to have a substructure consisting of six microcylinders surrounding a single central cylinder, all embedded in an electron-dense matrix. After uranium and lead staining, the substructure consists of concentric electron-lucent and electron-dense regions. The substructure of the central fibers may be the same. The outer arm of the A subfiber is pentagonal in shape; the inner arm is rod-shaped. The lumen of the A subfiber contains a body which seems to be associated with the inner arm. It is suggested that the visualization and interpretation of substructural detail depend greatly on electron staining techniques.