496 THE GENERAL PRINCIPLES OF ZOOLOGY 



study of facts, he not infrequently followed the theories or asser- 

 tions of others without verifying them ; he believed in the the- 

 ory of spontaneous generation, or abiogenesis, as it is sometimes 

 called, not only for small animals, but for such as eels, frogs, and 

 snakes as well, and his knowledge of anatomy as well as of 

 physiology was very incomplete. He was not the first to believe 

 in a possible evolution of higher animals from lower ; this theory 

 was held by other Greek philosophers both before and after 

 him. That he was fundamentally a lover of nature is very ap- 

 parent in his writings, and it is interesting to find him urging the 

 study of the lower animals, as when he says : " Hence we ought 

 not with puerile fastidiousness to neglect the contemplation of 

 more ignoble animals ; for in all animals there is something to 

 admire, because in all there are the natural and the beautiful." 



No other writer of any note on natural history appears in the 

 classical period until Pliny the elder (23-79 a.d.), the Roman 

 general. His lengthy work on this subject was, however, a 

 compilation of stories and reports from many sources, and as he 

 inserted indiscriminately the fabulous and the true, his writings 

 are of no scientific value. He further took a very retrograde 

 step in substituting for the natural classification of Aristotle one 

 based on habitat, so that he recognized land animals (terrestria), 

 aquatic animals (aquatica), and flying animals (volatilia). 



In the next century Galenus (130-200), a celebrated Greek 

 physician and anatomist, who lived for some time at Rome, con- 

 tributed somewhat to the knowledge of mammalian anatomy, 

 but he is the last of the real scientists until the sixteenth cen- 

 tury. Throughout the middle ages scientific investigation in 

 natural history was unknown ; the book on zoologv at that 

 period dealt with such animals as the phoenix, the dragon, and 

 the unicorn. Many religious teachers, however, wrote exclu- 

 sively on the philosophical side of the subject, the general 

 tendency, culminating in the works of Augustine (353-430), 

 being an inclination to the theory of the Greeks of spontaneous 

 generation, and a belief in a gradual development of life from 

 the lower to the higher, — in short, a suggestion of evolution 

 in place of the literal interpretation of the Mosaic account of 

 creation. Augustine being a teacher of acknowledged author- 

 ity, his beliefs had numerous followers throughout the middle 





