According to scientists, the octopus evolved from a creature very similar to the modern conch.  In other words, the octopus was a shell fish, but lost it's shell.  So how did this help the octopus?  Well, lets compare the octopus and the conch.

 

Conch	Octopus
Shell protects from attacks by some enemies	No shell, must hide under rocks to sleep with some protection
Moves very slowly	Moves much faster, and can take off very fast when threatened
Can do little to protect itself when attacked	Can use its tentacles to fight off enemies and to catch food

So, while the conch has one advantage, it seems the loss of it's shell and further evolution gives the most advantage to the octopus.  In fact, in the Bahamas, where conch is a popular dish, wild conch has practically disappeared and most of the conch sold there now comes from conch farms. 
So what does all this have to do with spiritual development?  Quite a bit actually.  Many people are like the conch.  They want to hide in a shell and feel protected and secure, even when it's false security.  This often prevents them from trying new things, taking chances and, in doing so, learning how to grow spiritually.  So if you want to grow spiritually, you need to take some chances and get out of your shell of conformity and safety occasionally.