Jan Stock was born in western Amsterdam 22 February 1931, the only child of Jan Hendrik Stock, a bank clerk, and Elisabeth Stock-Knevel. He exhibited an early interest as a child in living things, raising plants on a back balcony of his parents apartment and collecting animals during family excursions to the beaches at Zandvoort. However, it was in his early teens in the Hoogere Burgerschool that his interest in biology blossomed where he achieved perfect scores in natural history on his final examinations. He entered the University of Amsterdam in 1948 to pursue his studies of biology and worked under such figures as Profs. L.F. de Beaufort and H. Engel – his predecessors in the chair of Special Zoology – as well as Profs. J.E.W. Ihle and E.J. Slijper. It was Ihle in fact who first encouraged Stock to take up the study of pycnogonids, the sea spiders, a group in which he made some of his initial scientific contributions. His first scientific articles date from the student years and appeared in Het Zeepaard, the journal of the beach research groups of the Dutch Youth-Union for Nature Studies and the Dutch Natural History Society. These attracted him to the attention of De Beaufort who gave him a job as a curatorial assistant in the Zoological Museum of Amsterdam in 1950 with duties in the then poorly organized collections of marine invertebrates. He set up a card catalogue of the collections, tracked loans of museum materials to other researchers, and identified specimens for members of the public. It was through this last activity, when he received from the National Fisheries Institute (then at Bergen-op-Zoom in the Dutch province of Noord-Brabant) some parasitic copepods afflicting mollusks, that Stock developed another of his research interests, the taxonomy of copepods. His first real scientific papers date from that year.