The survival of the fittest notion is on of the most misunderstood points of evolution. It should be survival of the most adapatable.
The notion of the fittest is misused by almost everyone.
Just a point that really bugs me.
Your statement is quite imprecise, actually. Survival applies to individuals, whereas adaptation is a multi-generation genetic sort of thing -- they're not the same concepts.
Probably the most accurate statements are also the most unsatisfactory: "survival of the ones that didn't die before they mated;" or, "survival of the ones who produced the most offspring."
The point being that "lack of fitness" is not the only reason that things die or fail to reproduce; and "fitness" is not the only reason things survive and reproduce.
The Theory of Evolution can be restated along the lines that certain characteristics provide a statistical advantage, not for survival per se, but rather for successful reproduction. (The idea is supported by the existence of many species for which one or both parents die immediately after reproduction....)