Evening star., 1950-12-25
Worlds S Lost Week End
80 Million Years Long
New 'coIendor' Shows Blank
In Record of Geologic Time
By Thomos r. Henry

There is q 1oSt week end" in earth's
history-a period of 80 million years.
This is brought out in new calendar
of the planets ages just issued by the
Committee on the Measurement Of
Geologic Time of the National Research
Council. The calendar is compiled from
the most recent measurements of the
age of rocks by the rate of transmutation
of uranium into lead and of the rare
radioactive element rubidium into
Strontium.
nj this compilation the beginning Of
the Cambrian period, when the first
fossils appear in rocks formed from sea
bottom muds. is fixed at about $40 mil
lion years ago. The dominant animals
were crablike creatures. although not
remotely related to present-day crabs,
the trilobites. This period, according to
the new calendar of the rocks, lasted
from 10 million to 80 million years, when
the trilobites gave way to other dominant
life forms in the ancient seas.
Desertlike Stretch.
Below the Cambrian is a desertlike
stretch Of time, the -Cambrian,
throughout whose rocks are found vague
traces of life processes and of sedimen-
tary rock formation. This is assumed
to start with the earliest tracable rocks,
limestone formations in Southeastern
Manitoba which are about 81 billion
years old. Evidence suggests that this
was long after the formation of the solid
crust of the planet. The age of the
crust has been calculated from other
data at about maximum of $3.50, ,000, 900
years.
The pre- e-Cambrian is calculated on
fairly reliable evidence to have con-
tinued for is billion years, more than
twice succeeding time.
But between the end of the pre-
Cambrian, about $50 million years ago,
and the start of the Cambrian there is a
30-million-year gap concerning which
no evidence has been obtained. 1t is as
if these milleniums had been dropped
out of time
Naturally, reports DR.. j. Putnam
Marble, chairman of the committee, all
calculations of geological eras are subject
to considerable error and it is difficult to
calculate the length of the first six
geological periods with an accuracy
closer than 10 million years.
A gap of three-fold this figure, how
ever, remains inexplicable.
Some Of the new antibiotics, medi-
c.ne's most potent weapons against germ
infections, may effect heredity.
This unexpected development has been
reported to the American Genetic Asso-
citation by DR.. G. B. Wilson, associate
professor OF botany at Michigan State
College.
BY exposing lily bulbs in mixtures of
these substances and water he has Sc
cured effects similar to the early states
of those produced by colchichine, most
potent of chemicals with which it has
been possible to produce new types Of
plants and, possibly, animals.
Essentially, it has been possible to
produce preakages in the chromosomes.
the strings of genes, basic units of
heredity. These genes then are thrown
into new arrangements.
PenicilIion Works, Too.
This applies. but to a very minor
extent. with immersion in a mixture Of
penicillin, the most abundantly used of
the antibiotics. 1t is true, however that
alterations are somewhat more frequent
than in control bulbs not exposed to the
substance.
Somewhat more marked are the effects
of streptomycin. In all concentrations
of the drug the chromosomes appear to
be markedly shortened Much more
notable is the effect of neomycin, an
other derivative from a mould. when
concentrations greater than Is parts per
million are used. Not only do the
chromosomes seem to be shorter than
normal but there is a relatively high
frequency OF other deviations from
normal.
Most interesting was actidione, derived
from the same organism as streptomycin.
1t is quite poisonous and has not yet been
used in medicine. It had the most pro-
nounced effects not only in the lily bulbs
but on rye and bent grass seedlings.
The roots were highly affected.
The studies to date, DR.. Wilson says,
indicate at least the possibility Of far
reaching effects on the cytoplasm Of
living things. At the present stage, how
ever, it is unlikely that human beings
ever will receive amounts which seriously
will affect heredity.