The 200th anniversary of the Department of Zoology of St. Petersburg State University and the 150th anniversary of its daughter Department of Invertebrate Zoology are decent reasons to consider the important historical phenomenon. The history of the Department is the story of development of Zoology, the story of revolutionary changes in society. But, at the same time, it is the story of the continuity of generations of zoologists. The article presents a brief historical review of two centuries, but also contains elements of analysis: the long and fruitful existence of the zoological department makes it possible to trace the main trends in its development. Many of its features are likely to be common to the logic of evolution of “biodiversity departments”, but of course, each department with a long history is unique. Here is a historical case study. I hope that reflection on historical events can help identify the trends and even the reasons of the Department’s sustainability throughout this considerable time interval.