526 
The Ohio Naturalist. 
[Vol. VI, No. 7, 
Fig. .5. A continuous spirem singly split. The spirem may be 
traced by focusing from the granules at the right around the elbow above 
and back on the left side where after crossing twice it turns and passes 
under the elbow to the granule next the starting point. In addition to 
this there can be traced from the first granule, a loop passing under the 
other large granules where its relations cannot be made out. It is not 
impossible that this loop is not linin at all but some cytoplasmic conden- 
sation. It is not like the rest of the spirem in appearance. On sujicrfi- 
cial examination the right portion might be mistaken for an end view of 
a tetrad with bridges between the rods but its relations to the whole 
clearly negate any such possibility. 
Fig. 6. A split spirem doubled on itself to form the two tetrads. 
It has already broken apart at the upper end of the right tetrad leaving 
two loo'se ends, connected by a faint strand of dense sytoplasm. 
h'ig. 7. Spirem in which one strand is twisted entirely around the 
other in a manner impossible in a split rod. The two ends of the loops 
are beginning to break apart or perhaps have already broken but remain 
in close contact. 
Fig. >S. One tetrad nearly formed, the other lagging. The relations 
of the four rods to the right are not possible to make out precisely. On 
the left the loop of the original spirem is still evident. This shows the 
longitudinal split faintly in the distal end. Such a figure as this might 
easily be interpreted as due to a double split. The loop looks at hrst 
sight like the incompletely separated ends of a longitudinal split. But 
at the point of junction the distal (left) arm turns up and then bends 
down to meet the other which in like manner turns down and then up 
making a rounded loop perpendicular to the plane of the paper. One 
arm of the loop is also much shorter than the other but dees not seem to 
be cut off or disturbed. 
Fig. 9. A nucleus in which one of the two tetrads is much more com- 
pletely formed than the other. The right tetrad is seen to be composed of 
four rods two above the others. The spirem has completely broken across 
between the two arms of the loop and in one side the longitudinal split 
is also complete while in the other there remains a bridge across between 
the two portions. At the base of this tetrad both arms are seen to be 
continuous with the spirem which starting from one arm bends around and 
is twisted on itself in the position of the left tetrad, returning to the 
second arm of the right tetrad. In the parallel strands near the right 
tetrad are seen two pairs of small granules which may be chromatin or 
merely thickenings of the linin thread. Were it not for the evidence of 
the rest of the loop these might be taken to have arisen by a longitudinal 
split but such an interpretation is clearly impossible of the twisted spirem 
of which they are a part. 
Fig. 10. A continuous split spirem of almost the same age as figure 
(), in which the tetrads are clearly forshadowed though not yet differen- 
tiated. Contraction with consequent obliteration of the chromatin gran- 
ules has gone further than in fig. (1, but the arm of the tertads have not 
approached closely nor has any break occurred. The linin connections 
which are very evident were largely lest in reproduction. 
Fig. 11. A nucleus in which the four chromatids of each tetrad are 
clearly visible. The double linin thread may be traced into the overlying 
chromatids of the right tetrad which bend back and down to become con- 
tinuous with the two underlying chromatids which in turn are contin- 
uous with the second pair of strands of linin thread. The connections 
of the left tterad with these linin threads is so indistinct as not to be exactly 
traceable. The left tetrad is in such a position that three of its chroma- 
tids are visbile while the fourth may be traced by focusing down. The 
different chromatids are much connected by bridges. 
Fig. 12. A pair of tetrads fully formed and lying in the maturation 
spindle, showing the characteristic angle between them. 
