A Comparative Study of the Chromosomes etc. 
253 
with the longitudinal axis of a tubule, At the tip of the sections may be 
seen a single spermatogonium in anaphase. Figure 11 (Plate XVIII) 
shows part of the nucleus of the apical cell, and processes of cytoplasm 
niay be followed to the degenerating cyst on the right. Figure 12 (Plate 
XVIII) shows part of the cytoplasm of the apical cell, likewise degene- 
rating cells at both right and left of it. In Figures 39—44 (Plate XIX) 
are shown types of degenerating cells. They closely resemble figures 
by Flemming (’87) of degenerating ceUs in the testis of Salamandra, by 
WiLcox (’95) in the testis of Cicada, by Schäfer (’07) for Dytiscus and 
by Büchner (’09) for Oedipoda; but I do not think that one is likely 
to confuse tliem with synizesis, as clainied by Büchner (’09). 
The younger cysts are spherical and the spermatogonia are roughly 
conical, their apices pointing toward the center of the cyst (Plate XIX, 
Fig. 29). Düring the entire quiescent period there remain in the nucleus 
deeply staining cliromatic Centers, which lie dose to the nuclear mem- 
brane and are connected with one another by achromatic fibers. Figures 30 
and 31 (Plate XIX) are optical sections of a single spermatogonium at 
different levels. After a series of counts, I am convinced that these 
chromatic Centers correspond in number to the spermatogonial chromoso- 
mes, and represent the Centers about which the chromosomes form pre- 
ceding the spermatogonial divisions. This is also substantiated by the 
manner in which the chromosomes arise in the prophase, these resulting 
from condensations of the chromatin at particular points in the nucleus, 
rather than from the Segmentation of a spireme thread. While the chro- 
matin aggregates into comparatively short, weU defined, longitudinaUy 
split rods, apparently independent of each other, still the rods remain 
in Connection with one another by means of linin fibers, throughout the 
entire process of mitosis. The prophase chromosomes can never be con- 
fused with the chromatin of early stages in the growth of the spermato- 
cytes, which exhibits long thin chromatic threads. In the spermato- 
gonial mitoses the halves of the chromosomes separate simultaneously, 
the daughter chromosomes never adhering by theii- ends. 
The number of chromosomes in the spermatogonia of E. curvata is 
nineteen (Plate XIX, Figs. 32—36), as was contended by Boring (’07). 
Here, also, the large pair, the macrochromosomes, is the most striking 
characteristic. They are usually a little more curved than those of E. bino- 
tata, but are of practicaUy the same size, judging from camera drawings. 
Here also the second largest pair may sometimes be distinguished, but the 
remaining fifteen cannot be paired with accuracy, nor is it possible here to 
distinguish the single unpaired chromosome by its size or staining reactions. 
