148 Notes, i. 1—3. 



their several works by chance and without order Creation is mixed, and is the 



result of an union of necessity and mind." 



27. "For, as was said on an earlier occasion, each thing made by nature has certain 

 fixed and definite characters ; and these it has not because it is developed with them, 

 but rather it is developed with them because it has them ; for the essence precedes ^nd 

 determines the development, not the development the essence. Physiologists of old 

 held a contrary view. For they did not perceive how many causes there are ; but 

 recognised only the material and the motor causes, and even these confusedly, while 

 the formal and the final cause entirely escaped their notice " [D. G. v. i, 5). 



28. As to Aristotle's notions of the mechanism and use of respiration, cf. iii. 6, Notes 3, 6. 

 (Ch. 2.) 1. Alluding to Plato's method of dividing downwards until by successive 



bifurcations the infima species is at last reached. Examples of this method, abscissio 

 infiniti, will be fo.und in the Sophistes and Politicus. These ai;e apparently the 

 "published dichotomies" of which A. speaks; and it is to them that his criticisms 

 in this and the two next chapters have immediate reference. The great interest of 

 these chapters to the biologist lies in the evidence they give that the idea of natural 

 classification had occurred to Aristotle, their whole drift indeed being to uphold the 

 claims of natural as opposed to artificial systems. 



2, Not a well-chosen example. For Cloven-footed does not necessarily imply Two- 

 footed, as many quadrupeds have free toes. But A. is probably thinking only of Birds, 

 which he subdivides into Web;footed and 'Cloven-footed ; using the latter term as it is 

 used in the following passage : " Great variety of water- fowl, both whole and cloven- 

 footed, frequent the waters " {^Ray on Creation). ' 



3. By the water-animals with many feet are meant the Cephalopoda and certain 

 Annelida confounded by A. with Myriapoda. Cf. iv. 5, Note 70. 



(Ch. 3.) 1. What we call the wing of an insect, A. called the feather, which he 

 distinguished from the feather of a bird by its being undivided into barbs (iv. 6, Note 6). 



2. The argument is this. If we start with such a dichotomy as A and Not A, there 

 must be subdivisions of each of these. Let us say B and C are the subdivisions of A, 

 while D and E are the subdivisions of Not A. A then is a differentia common to 

 B and C, but though common to them it applies really to each in a different manner. 

 Not A '\% z. differentia common to D and E, and as there are no possible diversities 

 of Not Af it belongs to D and to Em exactly the same sense. In other words the 

 groups D and E have a common undifferentiated element, something therefore which 

 cannot be part of their essence. 



3. The wild dogs of India were supposed by A. to be a cross between the Dog and 

 the Tiger. Cf. II. A. viii. 28, 14 ; D. G. ii. 7, 9. 



4. The following appear to be the chief rules recognised by A. in the classification of 

 animals. 



a. The groups must be formed by consideration of the sum of the characters, not by a 

 single character arbitrarily selected. 



/3. Those characters are the most important which have guided mankind in generaf in 

 forming groups, to each of which they have given a popular name : in other words the 

 external characters. 



7. There are however natural groups, which are founded on other characters, and 

 which have been confounded popularly with alien groups owing to their external similarity, 

 e.g. Cetacea. 



8. When the individuals in a group are precisely alike in all theiV parts, the group is a 

 species (i. I, Note 2). A number of species may resemble each other in all their parts 



