Edward Turner Bennett was an English zoologist, and the 2nd secretary of the society, in post from 1833-1836.
William Yarrell was a zoologist. He was one of the original members of the Zoological Society of London and was a founder of the Royal Entomological Society. He was ZSL Secretary from 1836-1838.
John Barlow was was an Anglican priest. He was ZSL Secretary from 1837-1838, after which he spent many years at the Royal Institution.
William Ogilby was a zoologist. He is perhaps best known for this work around the classification order of cheiropoda, linking mammals who had hands. He was ZSL Secretary from 1839-1847.
David William Mitchell was a zoologist and illustrator. He was responsible for the construction of the fish house - the first public aquarium - in 1853. He was ZSL Secretary from 1847-1859.
Philip Lutley Sclater was an English zoologist and lawyer. He is best known for his work on ornithology. He was the longest serving ZSL Secretary, for 42 years between 1859-1902. In this time he corresponded with countless people around the world, and these letters are the ones that are extant.
William Lutley Sclater was a zoologist and the son of previous ZSL Secretary, Philip Lutley Sclater. He himself was only ZSL Secretary for 1 year in 1903, before Peter Chalmers Mitchell was selected for the post.
Peter Chalmers Mitchell was a Scottish zoologist, and ZSL Secretary from 1903-1935. He was responsible for founding Whipsnade Zoo.
Julian Sorell Huxley was an English evolutionary biologist, eugenicist and internationalist. He was ZSL Secretary from 1935-1942, in which time he introduced Pet's corner (the children's zoo) and Zoo Magazine.