THE BEGINNINGS OF LIFE. 1 7 3 



origin. The nature of the living matter, whether animal 

 or vegetal, was regarded, even by many ancient philo- 

 sophers, as an accident dependent upon the influence 

 of particular sets of conditions. As we have seen^, 

 Aristotle thought that plants might be engendered by 

 the tissues of animals, and, on the other hand, that 

 certain lower kinds of animals might take their origin 

 from and within the substance of plants. Ovid, there- 

 fore, was but reproducing an actual belief of his time 

 when, in his exposition of the Pythagorean philosophy, 

 he wrote : — 



' Si qua fides rebus tamen est adhibenda probatis ; 

 Nonne vides quaecunque mora fluidove calore 

 Corpora tabuerint, in parva animalia verti? 

 I quoque, delectos mactatos obrue tauros; 

 Cognita res usu; de putri viscere passim 

 Florilegse nascuntur apes.* 



And, under the particular form alluded to by the poet, 

 the doctrine has been handed down by some even to 

 our own times. The higher organisms, both animal 

 and vegetal, after their death, and during the process 

 of putrefaction, have been supposed to be capable of 

 giving rise indifferently — and often at the same time — 

 to certain of the lowest animals and of the lowest 

 plants. 



Before inquiring into the nature of the more recent 

 and exact information obtained upon this subject, 

 it will, we think, be well to cite the opinions of a few 

 ^ See vol. i. p. 253. 



