- last post: 01.01.0001 12:00 AM PDT
The theory that grunts and jackals are what make up the Carrier forms are speculations on the parts of the marines at Alpha Base in the book The Flood. Whether or not this is the whole story or not, we don't know. However, if you look at the in game models, the legs of the carrier forms are much longer than those of grunts or jackals. I think it is more likely that a Carrier form is created from a combat form that "consumes" one or more grunts and/or jackals (or anything to gain extra biomass), around which the new infection forms are created.
The Flood infect beings by "rewiring" their nervous system. Hunters are describe as "collectives of worm-like organisms united under a common consciousness" (taken frmo the official Halo 2 strategy guide), they most likely do not have the type of nervous system that would allow for them to be infected by the Flood. Brutes might have a decent chance of getting infected, but since we didn't see them in Halo 2 (and there wasn't really a specific reason not to, as far as I know), I don't think we'll see them in Halo 3.
Other new forms might be entirely possible, however.