Trophy Description:Find all 'secret' collectibles.
Missable

There are 5 secret collectibles in the game. One in each of the 5 levels. The trophy will pop once you pick up the last one. The secret collectibles do show up in free play, though they might not count towards the trophy so I've put it as missable. To be safe, get them all in a single player playthrough. The video below is of Alien Breed: Evolution which is just the 360 version of this game.

Thanks to RunOrShoot on youtube for making the video.