Complex sentence: It can often be hard to tell, however, what is a colonial protist and what is a multicellular organism in its own right, as the two concepts are usually indistinguishable, and this problem plagues most hypotheses of how multicellularisation could have occurred.
Split into simpler sentences: It can often be hard to tell, however, what constitutes a colonial protist, and what is a multicellular organism in its own right, as the two concepts are usually indistinguishable. This problem plagues most hypotheses of how multicellularisation could have occurred.