 Why was the large Kallerian not chosen for the journey?
The aliens came in every shape and form, in all colors and textures—and all of them eager for a Corrigan contract. But just because we needed him didn't mean we had to be extravagant in hiring him. He was followed by a roly-poly blue-skinned humanoid from Donovan's Planet, four feet high and five hundred pounds heavy. Before then, anyone could visit Earth. After the gate clanged down, a non-terrestrial could only get onto Sol III as a specimen in a scientific collection—in short, as an exhibit in a zoo. At the same time, we had turned away a dozen ursinoids, fifty of the reptilian natives of Ghryne, seven Sirian spiders, and no less than nineteen chlorine-breathing Procyonites wearing gas masks.
 There were already four Kallerians in inventory.
 There were already four Kallerians in inventory.  His species was too large to travel in the group.  He was argumentative during the interview process.  His payout demands  exceeded their budget.