The officer class of the Army and Navy provided a way to ascend this hierarchy; it was commonly the Ship's Surgeon who collected specimens on voyages, and Robert McCormick had secured the official position of surgeon on Beagle after taking part in earlier expeditions and studying natural history.
A clase dos oficiais do Exército e Mariña proporcionaba un modo de ascender nesta xerarquía; era común que o cirurxián do barco coleccionase espécimes nas viaxes, e Robert McCormick asegurárase a posición oficial de cirurxián no Beagle despois de ter formado parte de expedicións anteriores e ter estudado historia natural.