8 PRINCII'LES OF ANIMAL BIOLOGY 



have concerned themselves with biology so much in advance of other 

 peoples. But the Greeks were of a philosophical bent, they preferred 

 theorizing to the prosaic collection of facts. The origin of things in 

 nature was particularly fascinating. Thales, an astronomer, conceived 

 all life to have originated in the ocean, an idea that has its supporters 

 today. Anaximander supposed that living things were first produced 

 by the drying crust of the earth, which had been in a liquid state; and 

 curiously enough, man was held to be the first of these products. He also 

 believed that animals, of the kinds we know today, are produced out of 

 inorganic matter, as eels from mud. This doctrine of the origin of living 

 from non-living matter, known as ahiogenesis, was held for centuries in the 

 crude form adopted by the Greeks, but has been long since disproven 

 and abandoned. Fossils were recognized as animal remains by Xeno- 

 phanes, who correctly inferred from them that water once covered the 

 land. Empedocles made some observations on embryonic development, 

 the earliest ones, indeed, that are recorded. He also evolved a theory 

 of the origin of animals, according to which heads, arms, trunks, necks, 

 eyes, etc., were formed separately, and were kept apart at first through 

 the force of hate. Then love triumphed, he supposed, and these parts 

 began to combine. The combinations were purely fortuitous, and most 

 of them were incapable of maintaining themselves. Others were more 

 fortunate, and formed the animals now found on earth. Empedocles 

 thus enunciated a crude form of theory of the survival of the fittest. 



The Greek writers so far mentioned all lived in,^ML43£ior to, the fifth 

 century before Christ. Their ideas were a curious mixture of truth and 

 error, mostly the latter. A few have proven correct, or at least still 

 have some support. But it can hardly be too strongly stated that these 

 earliest notions, even when correct, were often not necessary deductions 

 from observed facts, but happy conjectures. 



Aristotle. — One of the Greek philosophers stands out in high relief, 

 by reason of his correct methods and superior accomplishments. This 

 was Aristotle, who lived in the fourth century before Christ. A portrait 

 of him is given in Fig. 1. Aristotle was a man of high intellect and 

 one of the greatest philosophers of ancient times. He was a pupil of 

 Plato, and the teacher of Alexander the Great. Like other scholars of 

 his time, he dealt with a great range of subjects and published hundreds 

 of works, many of which are lost. He wrote treatises on philosophy, 

 psychology, metaphysics, rhetoric and politics, but assumed the role 

 of leader most distinctly in natural history. If one were to judge 

 Aristotle by present standards the great philosopher might seem less 

 notable, but it must be remembered that he was a pioneer, and that he 

 lived at a period in the development of science when errors and crudities 

 were to be expected. However, he recognized the things of importance 

 and he adopted the right method in trying to advance knowledge. He 



