The Ohio Naturalist. 
[Vol. XV, No. 7, 
5*0 
division in the first reduction karyokinesis was again reported 
essentially similar to that described for Lilium philadelphicum. 
At the time this paper was written, the writer still knew nothing 
of Mendelian heredity. The following statement was made in 
regard to the probable individuality of univalent chromosomes in 
the bivalent chromosome—“Altho there is no way known to the 
writer of tracing the origin of the reduction chromosome in this 
nucleus to two previous ones, theoretically one might consider it pos¬ 
sible that the reduction chromosome represents two normal chromo¬ 
somes, and the closed loop the point where the usual transverse 
break should have taken place.” Namely, when the double num¬ 
ber of chromosomes are formed from the continuous spirem. 
‘‘But such a process would necessarily result in a qualitative 
division.” 
That the bivalent chromosome is actually made up of a pair 
of univalents, one from the maternal and one from the paternal 
side, was definitely shown to be the case by Montgomery 4 
in 1904. Thus the general facts of the reduction division had 
been worked out and there was only needed a comparison of the 
results with the rediscovered Mendelian heredity. Such com¬ 
parisons were of course, made by many writers. 
The cytological evidence may be summarized as follows: 
the chromosomes are self-perpetuating bodies which have a defi¬ 
nite individuality of size and shape which can be recognized in 
many species. This individuality is not lost or impaired when 
the chromosomes spread out in the form of a network in the 
resting nucleus nor when they join end to end to form a con¬ 
tinuous spirem. The haploid number of chromosomes represents 
a normal complement or set, each of which developes a specific 
attraction and unites with its corresponding or synaptic mate 
in the prophases of the reduction division (synapsis period) 
and each pair is segregated according to the law of chance to 
the two poles of the spindle. When at a future period gametes 
are formed and fertilization takes place, the univalents do not 
fuse but retain their separate existence during the entire zygotic 
stage of the organism. The pairing of corresponding univalents 
is of fundamental importance; for without such a process heredi¬ 
tary ratios would be much more complicated than what they 
really are, even tho the reduction division proceeded normally. 
The chromosomes representing synaptic mates may have absolute¬ 
ly similar hereditary factors and thus be homozygous and the 
4. Montgomery, Jr. T. H. Some Observations and Considerations 
upon the Maturation Phenomena of the Germ Cells. Biol. Bull. G: 137-158. 
See also Montgomery: The Spermatogenesis of Peripatus (Peripatop- 
sis) balfouri up to the Formation of the Spermatid. Zoolog. Jahrb. 14: 
1900 and Montgomery; Mitosis in Amphibia and its General Significance. 
Biol. Bull. 4: 259-269, 1902. 
