ISIS. 11 
WILCOX : SPERMATOGEN 
o dumb-bell figures become associated in pairs (Plate V. Figs. 229, 
42, 243). Each of the six groups (Diagram 6) thus formed has the 
eis of four chromosomes, each dumb-bell being equal to two chromo- 
somes (Plate IV. Fig. 178, Plate V. Figs. 242, 243). These quadri- 
valent groups may be formed by the approximation of the pairs of dumb- 
bells in one or the other of two ways. Either they become arranged 
quite irregularly (Plate III. Fig. 116, Plate V. Fig. 229), or the pairs 
may at first lie across each other at right angles, and later come to be 
parallel (Plate V. Figs. 229, 242, 243). A comparison of the draw- 
ings last mentioned will show how by the fusion of the ends of the two 
parallel dumb-bells a ring results, such as is shown in Plate IV. Figs. 
178, 179, 181, 
Dy a slight variation in the time at which the massing of the chroma- 
tin granules takes place the process up to this point may pursue a course 
apparently quite different from that described. The chromatin granules 
of the original chromatin thread do not become massed into definite 
chromosomes as early as in the method just outlined. Consequently 
the transverse divisions result in the formation of twelve segments 
(Diagram 8) with very irregularly serrated edges. These segmenta asso- 
ciate themselves (Diagram 9) in pairs (Plate V. Figs. 201, 225, 227). 
They are either so closely applied to each other as to appear like single 
rods, or else show two rows of granules (Fig. 227), and thus give the 
same appearance that would have resulted from a longitudinal splitting 
of a single segment. The component halves of these six segments sep- 
arate from dos other except at their ends, and thus form rings, as in 
Plate IV. 
collect into bg chromosomes (Diagram 10). The result is, therefore, 
. 174. The granules scattered along these rings then 
the same as by the process first mentioned. 
This aecount of the formation of rings varies somewhat from those 
of vom Rath (93) and Häcker (93), and is entirely different from 
Brauer’s (93) account. These differences, as well as the points of agree- 
ment, will be discussed under the literature of the subject. 
The position of the chromatic rings at the equator of the spindle is 
shown in Plate V. Figs. 192-195 and 237-241, "The rings are always 
complete at this stage, and the first step in the metakinesis of the sper- 
matocytes consists in a separation of the rings into half-rings. With 
the iron-hoematoxylin method the majority of the spindles present the 
appearance of Figures 194, 195. The planes of the rings all pass through 
the axis of the spindle. Hence it is impossible to see that the chromo- 
somes are arranged in rings, except when the rings are turned broadside 
