Who are the General's pupils?

Zaroff's pupils are actually his prisoners, men who've been lured to the island by the manipulation of lights or simply shipwrecked. These are the men he will hunt.

"We'll visit my training school," smiled the general. "It's in the cellar. I have about a dozen pupils down there now. They're from the Spanish bark San Lucar that had the bad luck to go on the rocks out there. A very inferior lot, I regret to say. Poor specimens and more accustomed to the deck than to the jungle."