Reason for crossed projections in the nervous system?

[Kalman Rubinson]

Matt Jones (jonesmat at ohsu.edu) wrote:
: Here's one hypothesis I heard in an undergraduate class. I have no idea
: whether there's any evidence.

: Early swimming animals evolved crossed projections from the visual system
: to the motor systems, so that an object perceived on one side of the body
: would cause contraction of the muscles on the opposite side, leading to a
: swimming movement away from the object (escape).

That seems derived from Coghill's thesis in 'Anatomy and the Problem of 
Behavior' (1929).  He posited the need for crossed connections in a 
multicelled pre-vertebrate to convey chemical or tactile stimuli to 
contralateral effectors for avoidance.  From this, he builds a model of 
spinal cord organization.

Kal