ly a third of a Satog's body
space is occupied by its brain.

"Kalechi's civilization is based on an understanding of biological
processes and the means of their manipulation which is well in advance
of our own. This specialized interest appears to have developed from the
Satogs' genetic instability, a factor which they have learned to control
and to use to their advantage. At present, they have established
themselves on at least a dozen other worlds, existing on each in a
modified form which is completely adapted to the new environment.

"Our occasional contacts with Kalechi and its colonies during the past
two centuries have been superficially friendly, but it appears now that
the Great Satogs have regarded our technological and numerical
superiority with alarm and have cast about for a method to destroy the
Federation without risk to themselves. A weapon was on hand--their great
skill and experience in altering genetic patterns in established life
forms to produce desired changes. They devised the plan of distributing
Kalechi agents secretly throughout the Federation. These were to develop
and store specific strains of primitive organisms which, at an indicated
later date, would sweep our major worlds simultaneously with an
unparalleled storm of plagues.

"The most audacious part of the Kalechi scheme follows. Ninety-two years
ago, a Federation survey ship disappeared in that sector of the galaxy.
Aboard it was a man named Ohl Cantrall, an outstanding scientist of the
period. We know now that this ship was captured by the Great Satogs, and
that Cantrall, his staff, and his crew, were subjected to extensive
experimentation by them, and eventually were killed.

"The experimentation had been designed to provide Kalechi's
master-biologists with models towards which to work. They proposed to
utilize the high mutability of their species to develop a Satog type
that would be the exact physical counterpart of a human being and could
live undetected on our worlds for the several years required to prepare
for the attack. They were amazingly successful. Each group of cells in
the long series which began moving towards an approximation of the human
pattern was developed only far enough to initiate the greatest favorable
shift possible at that point in its genetic structure. Cell generations
may have followed each other within hours in this manner, for over six
decades.

"The goal of the experiment, the last generation issue