A ('omparative Stad}' of thc Chromosomes etc. 267 
corresponds to the line of unioii of the clironiosomes in syndesis. In this 
form, parallel to each other along their lengths, the two chromosomes 
forming this macrochromosome tetrad lie in the eqiiatorial plane of the 
spindle of the first spermatocyte division (Fig. G). Occasionally the 
macrochromosome tetrad enters the spindle with the chromosomes end 
to end (Fig. H). This is due to the 
loss of the ring form and is similar 
to the condition found generally 
in Enchenopa. In Figures G and H 
the same resnlt is attained; that 
is, whole chromosomes are separa- 
ted; but in Figure G it is by a 
longitudinal Separation and in Fi- 
gure H by a transverse Separation. 
Tetrads of both forms were found 
in neighboring cells of the same cyst. 
Before the first maturation di- 
vision of E. curvata, one can distin- 
guish in both sinears (Plate XX, 
Fig. 121) and sections (Plate XX, 
Figs. 101, 102) the macrochromo- 
sonie tetrad, eight small tetrads 
corresponding to sixteen small auto- 
somes of the spermatogonia, and 
the round compact ic-chromosome 
with linin fibers radiating from it. 
The a>chromosome does not usuaUy 
Show the future plane of division, 
but in smears (Plate XX, Fig. 121) 
it could sometimes be detected. 
Textfigxires B to H. 
Figs. B — H. The macrochromosome geminus in 
the first spermatocytes of Ämphiscepn bivittata. 
Figs. B — C. Macrochromosome geminus of early 
prophase, previons to longitudinal division. — 
Fig. D. Same at later stage showing longitudinal 
differentiation of the ends that are in contact. — 
Figs.E— F. Late prophase. Jf. microchromosome 
geminus. — Fig. G. Spindle of first maturation 
division. df. bivalent with both ends of components 
in contact. — Fig. H. Samo stage M. bivalent 
with only one end of components in contact. 
C. Comparison of the Growth Period and Tetrad Formation in 
Enchenopa binotata and Enchenopa curvata. 
A comparison of the behavior of the autosomes in the growth period 
of E. hinotata with that of E. curvata shows that there is a niarked simi- 
larity between the two species. The double threads of the bouquet stage 
are formed by the parallel union of pairs of leptotene threads. There 
are nine of these double loops in the bouquet stage, one of which is much 
longer than the others, and this doubtless represents the macrochromo- 
some paii’ Seen in the spermatogonia. This long loop forms a ring in the 
