VITAL rillNCIPLE. 25 



be controlled by the same laws which regulate the offspring 

 of uni vocal generation, as to form, structure and duration ; 

 and that the same beings should be able to continue, by 

 transmission, that life which they derived from accident ? 

 The most rational explanation which can be given of the 

 appearances of these plants and animals, in such places, is 

 derived from the consideration of the smallness of their 

 seeds or eggs, which may.be carried about by the winds, 

 and showered down along with the rains, so as to enter 

 with facility into every situation. They cannot, how- 

 ever, expand, unless in circumstances favourable to 

 their future growth. Thus the soil, in which alone the 

 beautiful little plant called Monilia glauca makes its ap- 

 pearance, is the surface of putrid fruit ; while the small 

 animal termed Vibrio aceti, requires for its growth, vinegar, 

 which has been exposed for some time to the air. This 

 view of the matter is still farther strengthened by the almost 

 indefinite length of time, during which, certain seeds re- 

 tain their power of germinating ; and certain animals, in a 

 torpid state, the faculty of reviviscence. 



We are thus led from the phenomena which organized 

 beings present, to reject the theory of equivocal genera- 

 tion, and to admit the important conclusion of HARVEY, 

 Ex ovo omnia. But the manner in which these eggs or 

 germs are produced, has furnished matter of curious spe- 

 culation to the physiologist. By some, it has been sup- 

 posed, that the germs of all the plants and animals that 

 have been, or ever shall be, in the world, were really all 

 formed within the first of their respective kind, to be 

 brought forth in a determinate order. This Theory of 

 Evolution, as it has been termed, is in a great measure the 

 result of microscopic observations, assisted by preconceived 

 views. There is one circumstance, however, which not 

 only receives no explanation upon the principles of this 



