This chapter deals with some problems linking biology and ontology. After a general survey of the most prominent ontological questions lying behind biology, the study case of biological boundaries is addressed. The scrutiny of the relevant literature shows that biologists speak of various types of boundary: perceptual, compositional, epithelial, cellular and sensu lato processual boundaries; all of them appear to be, in a way or another, flawed by some theoretical inconsistencies. So, a new concept of organismic boundary is introduced and discussed, by which the organismic boundary is the (concrete) part of an organism which spatially encompasses all and only the other (concrete) parts of that organism.