Incidentally, in terms of the original question, I'm inclined to think that if you identify a soul with individuality -- so that the Soul is what makes you "you" -- then there are many animals that do have souls in this way. Even birds can seem to have individual characters, although there is obviously a risk that I'm reading traits into them that aren't there (and my sample size is, so far, only six chickens).
There is probably some sort of fuzzy line between animals that are complex enough to have individuality, and those who do not. Don't know where the line is drawn, but at a rough guess most mammals and birds are on one side, and most insects on the other. On the other hand this doesn't coincide with animals that have brains and those that do not, so either there is some particular structure lacking in insects/ arthropods but not in mammals, or more likely this entire paragraph is filled with utter rubbish.