 Why was the Vegan not chosen to make the trip to Earth?
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. I had turned away three more ursinoids, hired a vegetable from Miazan, and said no to a scaly pseudo-armadillo from one of the Delta Worlds. And now, please, there are many applicants waiting—" You'd think it would be sort of humiliating to become a specimen in a zoo, but most of these races take it as an honor.
 The upkeep for the species was too much.
 There were too many of his kind already in inventory.  They were worrisome and difficult to work with.  He was much to large in size to accommodate.  The upkeep for the species was too much.