SPERMATOGENESIS OF EUSCHISTUS 745 
daughter (univalent) autosomes separate (figs. 95-97, 99, 100), 
the longitudinal split becomes much more pronounced upon each, 
appearing first as a deep indentation at the point nearest the 
equator of the cell. On polar view of an anaphase each autosome 
shows a constriction which is the split. In the second mitosis 
(figs. 102, 103) that follows without any interkinesis, the uni- 
valent autosomes divide along the line of this constriction, hence 
equationally, so that each spermatid receives a half of each of the 
six univalent autosomes (figs. 105, 106). In the equator of the 
second maturation spindle the autosomes are arranged usually 
in a circle around the pair of idiochromosomes (fig. 101). In the 
anaphases represented in figs. 104 and 107 to 109 individual auto- 
somes are not delineated but only the masses of them, for on 
lateral views it is difficult to make out their outlines; in fig. 110 
five autosomes are shown in each daughter cell, the sixth in each 
being obscured by one of the others. 
In the histogenesis of the spermatid the six autosomes early 
become irregularly massed in a circle around the idiochromo- 
somes; in fig. 111 they happen to be so closely massed that their 
individual boundaries cannot be determined, yet there isno fusion 
of them. Fig. 112 shows the delimitation of the young daughter 
nucleus by the formation of its membrane (in the stages of figs. 
110, 111 the chromosomes lie in a vacuole not yet bounded by a 
membrane), and the six autosomes in peripheral position around 
the central idiochromosome (d). From this time on the auto- 
somes remain strictly peripheral, until they finally produce the 
hollow cylinder of chromatin that composes the major portion 
of the sperm head. In fig. 113 the nucleus has grown in volume, 
and the autosomes have also become larger and less dense. Figs. 
114 to 117 illustrate succeeding stages, the nucleus attaining its 
maximum size and the autosomes becoming flattened against 
its membrane; fig. 117 shows four of the six autosomes, all that 
can be seen on profile, the remaining two being on opposite sur- 
faces. ‘The evidence is clear that the whole, or at least the major 
part, of the substance of the autosomes becomes peripheral, and 
that the larger bodies (D) that lie free within the nuclear cavity 
are derivatives of the idiochromosomes. By the stage of fig. 
