Career
In 1864 he began his scientific career as a préparateur of natural history under Jules Gosselet (1832–1916) at the Faculté des Sciences in Lille. He held the chair of zoology at Lille from 1888 to 1906, then served as chair of comparative anatomy and embryology from 1907 until his retirement in 1919. In 1888 he founded a marine biological laboratory at Le Portel that was associated with the Université Lille Nord de France.
His scientific work largely dealt with flatworms, nematodes, the phylaBryozoa and Nemertea, et cetera
He described a number of new species collected from Jean-Baptiste Charcot"s Antarctic expeditions. The following species are named after Hallez: Timea hallezi (Topsent, 1891) Procerastea halleziana (Malaquin, 1893) Scaptognathus hallezi (Trouessart, 1894) Obrimoposthia hallezi (Böhmig, 1908).
The genus Hallezia Sand, 1896 (Protozoa) is also named after him.
