Aristotle's biology unacquainted with Aristotle. And the very fact was again forgotten until Johannes Miiller brought it to light, and showed not only how complete was Aristotle's account, but how wide must have been his survey of this class of fishes to enable him to record this peculiarity in its relation to their many differences of structure and reproductive habit." ^* Turning from animals with blood to the bloodless animals, Aristotle continues his attempt to guide himself by the descending methods of reproduction^ which correspond with the lowering degrees of life and vital function in these inferior but still marvellously interesting creatures. Passing downwards through those Crustacea which he finds gener- ated from an imperfect ovum, he enters the realm of insects. These spring from the scolex or grub, which is metamorphosed, pass- ing through the chrysalis or pupa, into the perfect insect. ^° Lowest in the scale are molluscs and finally the zoophytes (sponges, Coelenterates) which are produced from generative slime or by spontaneous gen- eration. The last idea, of course, has been abandoned. Instead of giving the further details of
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