correct me if I am wrong, but evolution states that somewhere along the line life formed and evolved into more complex organisms....I do have that part correct, that is the theory, right? then form as many experiments that you'd like and see if an organism becomes more complex over time.
Evolution is direcitonless: it can lead to more complex organisms, or to simpler ones, depending on what's better suiting the environment. There isn't even much of an agreement on what's more complex: for one, a chimp is no less complex than a human. In fact, considering that we've been separate lineages for a few million years, we are remarkably similar with chimps: if we were bacteria, scientists would, probably, need genetic tests to even tell us apart.
In any case, if a bacteria were to develop so much as a cell nucleus, it would be orders of magnitutde more shocking and harder to accommodate within our current theories of evolution than the joint second coming and public gay marriage of Jesus Christ and the Flying Spaghetti Monster would be for you 
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How do you define "another" anyway? Animals change by discrete amounts in discrete aspects. It's not like a bacterium suddenly splits into two paramecia.
