 What is clear from the practice of the History of Animals is both the value of division and its limitations. Division by itself does not provide you with the axes of division; rather they are presupposed. Division does not give you animal kinds; as we saw in the previous section, one needs to turn to PA I 4 and HA I 6 for Aristotle’s thoughts on how those kinds are established. Something besides division is needed in order for a researcher to recognize theoretically significant kinds, such as cephalopods or cetaceans. Why group animals together based on their possession of four legs and the ability to give birth to living offspring (rather than eggs)? Certainly each of these traits is the product of a division, one of modes of locomotion and one of modes of reproduction. But those divisions do not tell you that animals with four legs that bear living young constitute a scientifically significant group.