Abstract
The spermatogonial metaphase of Hybris subjacens invariably shows 22 chromosomes (Figs. 1-4). All the chromosomes seem to be telomitic in the fibre attachment and slightly variable in their length. So far as the number and shape of the chromosomes are concerned, this species shows no marked difference when it is compared with the following four other species of the Ascalaphidae so far studied: Ascalaphus libelluloides, A. longicornis, Ogcogaster segmentator and Glyptbasis dentifera. An even number of chromosomes in the male diploid group suggests the existence of the sex chromosome constitution of the usual X-Y type.
There are found, at metaphase of the primary spermatocyte, 11 bivalent chromosomes (Figs. 6-7). Of these 11 elements, 10 are autosome bivalents and the other is the X-Y complex which is conspicuously recognized in the lateral view of the spindle, showing a remarkably precocious segregation into its components, X and Y (Figs. 8-9). Since the X is completely separated from the Y in the first division, two kinds of secondary spermatocytes are formed. The one group, the X-class, consists of 10 autosome dyads plus an X element; the other is the Y-class which contains a Y element with a similar complex of autosome dyads (Figs. 10-11).
The occurrence of elongated or V-shaped centrioles was ascertained in the spermatocytes of the present species. In the primary spermatocyte metaphase the two V-shaped centrioles, with their widely diverging rod-like arms, assume their respective positions at opposite poles (Fig. 8). Their form and behaviour in the spermatogonial and secondary spermatocyte divisions were briefly observed (Figs. 5, 9 and 12).
