What is the central idea of "Agassiz and the Fish, by a student"?

The central idea of "Agassiz and the Fish, by a student" is stated in the story.

"Facts are stupid things," he would say, "until brought into connection with some general law." - This is what Professor Louis Agassiz said after he let his students do a lot of observation on a number of fishes.

The facts that have been discovered in observing the fish are not relevant until it became connected to another bigger idea. Simply put, one needs to study the part and its various functions and uses to understand the whole.