Multiwell in-vitro fertilization plate

A plate assembly (10) for useful for in vitro fertilization procuedures such as receiving ova and for forming, evaluating, holding, manipulating and culturing embryos includes a base (12) with an apportioned top surface (14) and a sidewall (17). The top surface has a plurality of open wells (16) embedded therein for receiving ova to be cultured. The wells (16) are substantially cylindrical and have substantially flat closed bottoms (18) to facilitate microscopic examination of the well contents. The assembly includes a removable lid (20) for covering the top surface (14) of the base. The lid (20) is preferably divided into sections (22,23) comparable to the top surface portions (24,25) of the base. Each lid section (22,23) may be separately slidably moved between a closed position where the lid (20) covers a comparable portion of the top surface (14) and an open position where the top surface (14) is uncovered. The lid (20) has projections (60) which interact with grooves (58) in the base (12) in a cam/cam follower relationship to allow slidable movement of the lid sections (22,23) between the closed and the open positions while retaining the lid sections (22,23) to the base. The inside surface of the lid (20) and the base top surface (14) each have elements (50) which interact when the lid is in the closed position to form a tortuous path for gas interchange between the wells and the outside environment, thus substantially preventing microbial contamination of the wells when the lid is closed.