ORIGIN OF BRUTE MATTER. . 253 



humus have been found in several meteorites. To 

 the objection that these aerolites are heated while 

 passing through our atmosphere, Helmholtz replies 

 that this elevation of temperature may be quite 

 superficial and may allow micro-organisms to subsist 

 in their interior. But other objections retain their 

 force : — First, that of M. Verworn, who considers the 

 hypothesis of cosmic germs as inconsistent with the 

 laws of evolution ; and that of L. Errera, who denies 

 that the conditions necessary for life exist in inter- 

 planetary bodies. 



Hypothesis of Cosviic Panspermia. — Du Bois- 

 Reymond has given the name of cosmic panspermia 

 to a theory very similar to the preceding, formulated 

 by F. Cohn in 1872. The first living germs arrived 

 en our globe mingled with the cosmic dust that 

 floats in space and falls slowly to the surface of the 

 earth. L. Errera observes that if they escape by 

 this gentle fall the dangerous heating of meteorites, 

 they still remain exposed to the action of the photic 

 rays, which is generally destructive to germs. 



Hypothesis of Pyrozoa. — W. Preyer declined to 

 accept this cosmic transmigration of the simplest 

 living beings, nor would he allow the intervention of 

 other worlds into the history of our own. Life, 

 according to him, must have existed from all time, 

 even when the globe was an incandescent mass. 

 But it was not the same life as at present. Vitality 

 must have undergone many profound changes in the 

 course of ages. The pyrozoa, the first living beings, 

 vulcanians, were very different from the beings of 

 the present day that are destroyed by a slight 

 elevation of temperature. No doubt this theory of 

 pyrozoa, proposed by W. Preyer in 1872, seems 



