A Comparative Study of the Chromosomes etc. 
271 
Occasionally a longitudinal division of the a^chromosome was seen 
extending in the direction of the spindle (Plate XXI, Fig. 147). This 
is probably the normal Orientation of the a:-chromosome, but it may 
be that it is altered in the anaphase. As the chromosomes separate 
(Plate XXI, Fig. 150), the a>element, connected to the autosomes, 
is drawn nearer the axis of the spindle, and as the autosomes approach 
their centrosomes, it is located between the two chromosome plates, 
being elongated in the axis of the spindle and still showing plainly the 
connecting fibers (Plate XXI, Figs. 151, 152). The fibers stain darker 
than the interzonal filaments and are not necessarily parallel to them, 
often making a considerable angle with the axis of the spindle. NormaUy 
the a;-element is drawn nearer to one pole than to the other and is included 
undivided in one of the two second spermatocytes (Plate XXI, 
Figs. 153, 154). But in exceptional cases (Figs. 155—163, Plate XXI) 
the ic-element seems to be pulled with equal force by the fibers connecting 
it with the two groups of chromosomes. In some cases it is turned 90° on 
its axis (Plate XXI, Figs. 155, 157— 159) i®); in other cases it is simply 
drawn out in its normal Orientation (Plate XXI, Fig. 161) and divided 
(Plate XXI, Figs. 162, 163). 
Abnormal divisions of the a;-element have been described by Baum- 
gartner (’04) for Gryllus and lately by Stevens (’12b) for Diabrotica, 
Brunelli (’09) has suggested that the division described by Baumgartner 
was that of a lagging autosome pair and not of the rc-element. In E. 
curvata, however, the presence of the thick fibers and ,a consideration of 
the usual behavior of the a^element show that here the cases where 
this element is divided are caused merely by an exaggeration of normal 
processes. 
NormaUy ten chromosomes pass to one pole and nine to the other. 
Fach shows a longitudinal cleft in late anaphase and immediately enters 
upon the second division, as in E. Unotata. 
C. Comparison of the First Spermatoeyte Division of Enehenopa 
binotata and Enehenopa curvata. 
The behavior of the autosomes is aüke in both species. The gemini 
are elongated in the axis of the spindle. This is most clearly seen in the 
macrochromosome tetrad, and from the history of this pair of chromo- 
somes it is clear that the spindle fibers are inserted upon those ends of 
1®) Figure 159 was made from a smear slide, first dried and then fixed and stained. 
Oniy two fibers connecting with the a:-element remained visible after this treatment. 
Archiv f. Zellforscliung. XII. y8 
