[1] Attending Cambridge University, he was the first recipient of a studentship founded in honour of his supervisor Francis Maitland Balfour, who died in a climbing accident in 1882.
[2] Two years after graduating from Cambridge in 1880, Caldwell was appointed Demonstrator in Comparative Anatomy, working for Professor Alfred Newton.
With the assistance of the local Aboriginals, Caldwell set up camp on the banks of the Burnett River in northern Queensland, hunting for lungfish, echidna, and platypus eggs.
Mindful of the high cost per word, Caldwell tersely and now famously wired the British Association for the Advancement of Science meeting in Montreal: "Monotremes oviparous, ovum meroblastic".
[5] Platypus and echidna specimens collected by him were stored, but not catalogued, in the Cambridge University Museum of Zoology until they were rediscovered in 2022.