Appendix. 131 



produce a crop of serpents it is only necessary to pulverize one 

 and sow the powder as seed in the earth. He further averred 

 that fragments of plants falling into water became transformed 

 into animals, and he actually figured such animals in his book.* 

 Van Helmont, too, we find describing a mode for the artificial 

 propagation of mice, frogs, and eels. 



With our present knowledge of the mode of reproduction 

 in animals, we may perhaps smile at these crude and incorrect 

 notions, but we must remember that they were the best conclu- 

 sions then attainable, and they were the result of a truly scientific 

 but imperfect study of natural phenomena. Dr. Dalton well 

 says: " Aristotle represented in natural science, as in so many 

 other departments, the entire scope and successful activity of the 

 Grecian intellect. He occupied the position which was after- 

 ward held by the Buffons, Linnaeus, and the Cuviers of more 

 modern periods ; and it is certain that the opinions which he 

 expressed must have seemed reasonable from his point of view." 



It is not out of place to mention here some of the causes of er- 

 ror which are now apparent. The young of many of the lower vari- 

 eties of animals are so wholly unlike the parent, that it was 

 impossible to trace any similarity or relation between them, until 

 after patient observation the intermediate stages in their develop- 

 ment were learned. A familiar illustration of this is the larval 

 form of the common butterflies and moths, and the varied appear- 

 ances seen in alternate generation in insects. In their successive 

 developmental stages the animals will often inhabit different 

 localities, and in some instances even different elements. The 

 secretive habits of many of the oviparous and viviparous animals 

 precluded for a long time knowledge of their mode of reproduc- 

 tion. Some, as for instance fishes, will migrate long distances, 

 deposit their eggs quickly, and as suddenly disappear. After a 

 time the ova are hatched by the favoring influences of light and 

 heat, no parent animals being present in the vicinity. In others 

 the young on being hatched quickly betake themselves to a diff'er- 

 ent locality. Again, ova not infrequently lie dormant, as it were. 



Edinburgh Review, Vol. 89, p. 167. 



