Chiron the Centaur was the tutor of the young Achilles. The shape of this vase makes it hard to see, but that is Chiron there on the right, while on the left is King Peleus, entrusting his son Achilles into Chiron's care (if you look, you can see how Chiron's horse-body extends behind him and wraps around the vase). Here is a Latin poem Alciato wrote to accompany his emblem, with an English translation - you can see the emblem itself at the Memorial web edition of Alciato.
Heroum genitos, et magnum fertur Achillem
In stabulis Chiron erudiisse suis.
Semiferum doctorem, et semivirum Centaurum,
Assideat quisquis Regibus, esse decet.
Est fera, dum violat socios, dum proterit hostes:
Estque homo, dum simulat se populo esse pium.
Chiron is said to have instructed in his stables great Achilles and the sons of heroes. Whoever cares for kings should be a teacher who is half a beast, a Centaur who is half a human. He is a beast when he injures his comrades, when he tramples his enemies, and he is a man when he feigns devotion to his people.