Does a Druid animal companion increase in size as it increases in HD?

[Lord Sqwonk]

The chart shows all the stats, feats, special etc- but no mention of size. There is not manddatory starting size either.

The Bestiary says - "As a general rule, creatures whose Hit
Dice increase by 50% or more should also increase in size,
but GMs should feel free to ignore this rule if warranted
by the individual creature or situation."

Is there a rule for animal companion size and size increases?

Thanks

[Hama]

Yes there is...right in the animal companion rules in the core rulebook. For example, at druids 7th level, a tiger (large cat) companion increases to large...

[Dragonsong]

its in the descriptions of the animal options as to when or if they get a size increase.

Edit: ninja'ed

[LazarX]

animal companions get a one time increase as per the class feature description.