So I asked my GMs this question the other day, and there was some disagreement on it. Figured I'd give these boards a shot to help clear it up.
The wording for the discovery "Tumor Familiar" has the following line.
"An alchemist’s extracts and mutagens are considered spells for the purposes of familiar abilities like share spells and deliver touch spells."
This implies, to me, that if a companion entity is bonded with an alchemist with the "share spells" ability, it can make use of an alchemist's mutagen. Now, if an alchemist gains access to an animal companion (such as, for instance, via the feat Animal Ally) that has the share spells ability, would this still hold true?
Well... it does say "for the purpose of familiar abilities". So per the RAW it wouldn't fly, unless the companion's definition states it acts as a familiar for the purpose of sharing spells.