me than normal
it could fit into the remaining space in the cranial hollow. But
the brain is full-sized--it is just that part of it is missing,
absorbed by the symbiote."

"The frontal lobes," Brion said with sudden realization.
"This hellish growth has performed a prefrontal lobotomy!"

"It's done even more than that," Lea said, separating the
convolutions of the gray matter with her scalpel to uncover a green
filament beneath. "These tendrils penetrate further back into the
brain, but always remain in the cerebrum. The cerebellum appears to
be untouched. Apparently just the higher functions of mankind have
been interfered with, selectively. Destruction of the frontal lobes
made the magter creatures without emotions or ability for really
abstract thought. Apparently they survived better without these.
There must have been some horrible failures before the right balance
was struck. The final product is a man-plant-animal symbiote that is
admirably adapted for survival on this disaster world. No emotions
to cause complications or desires that might interfere with pure
survival. Complete ruthlessness--mankind has always been strong on
this anyway, so it didn't take much of a push."

"The other Disans, like Ulv here, managed to survive without turning
into such a creature. So why was it necessary for the magter to go
so far?"

"Nothing is necessary in evolution, you know that," Lea said. "Many
variations are possible, and all the better ones continue. You might
say that Ulv's people survive, but the magter survive better. If
offworld contact hadn't been re-established, I imagine that the
magter would slowly have become the dominant race. Only they won't
have the chance now. It looks as though they have succeeded in
destroying both races with their suicidal urge."

"That's the part that doesn't make sense," Brion said. "The magter
have survived and climbed right to the top of the evolutionary heap
here. Yet they are suicidal. How does it happen they haven't been
wiped out before this?"

"Individually, they have been aggressive to the point of suicide.
They will attack anything and everything with the same savage lack
of emotion. Luckily there are no bigger animals on this planet. So
where they have died as individuals, their utter ruthlessness has
guaranteed their survival as a group. Now they are faced with a
problem that is too big for their half-destroyed minds to handle.
Their personal policy has become their p