This article will introduce Yamamoto Bōyō's handwritten directory of his students, correspondents and Kyoto-based hikyaku couriers, covering nearly 25 years from 1830 to around 1856. The manuscript is composed of 305 items and includes 132 students and exhibitors to the bussankai (naturalistic annual workshops) held in the Kyoto school or by related naturalist groups in Osaka, Ise and Nagasaki. The naturalistic activities of the Yamamoto School depended on the hikyaku courier system which facilitated nationwide scientifi communication and exchange of specimens with students and related scholars in 41 ancient countries from Ōshū to Satsuma. In this article, the human network of this school is analyzed and described using the directory, here transliterated, and new documents discovered in the Yamamoto family archives.