Spermatogenesis in the Belostomatidae. II. The chromosomes and cytoplasmic inclusions in the male germ cells of Belostoma flumineum Say, Lethocerus americanus Leidy, and Benacus griseus Say

This paper contains a description of the appearance and behavior of the chromatin and chief cytoplasmic inclusions in the male germ cells of three species of Belostomatidae. There are eight spermatogonial chromosomes in Lethocerus americanus, twenty‐four in Belostoma flumineum, twenty‐eight in Benacus griseus. An XY‐pair of sex chromosomes occurs in each species. These are identifiable at every step in maturation in Lethocerus, but not in the others. A clear case of heteropycnosis occurs in Benacus. Parasynapsis is believed to be the mode of pairing of chromosomes in all three species. The genesis of three large atelomitic ring tetrads is described in Lethocerus. Chondriosomes are traced from spermatogonia to spermatids without a break in continuity. Spermatogonial chondriosomes are always granular. During the growth period filaments are formed, probably by fusion of granules, and these are sorted out in approximately equal numbers to spermatids. Benacus is especially favorable for studies on chondriosomes. Likewise, Golgi bodies have been traced throughout the process of maturation. They are minute granules in spermatogonia. During the growth period each becomes a flattened plate‐like body clearly differentiated into two materials. Dictyosomes are formed by fragmentation in the first prophase, and these are distributed to spermatids where they fuse to form an acroblast in each. Some minor cytoplasmic inclusions are briefly described.