310 THE BEGINNINGS OF LIFE. 



that these organisms had been derived in the ordinary 

 way from ova. The migrations and transformations of 

 entozoa in the bodies of different animals, and our 

 knowledge of the mode in which the embryos of cystic 

 and nematoid parasites are enabled to penetrate the 

 tissues, clear away many of these old difficulties. It 

 must be confessed, however, that the reality of such 

 new facts does not veto the possibility of the occasional 

 independent heterogenetic origin of some of these 

 organisms. I will merely state that such a mode of 

 origin is still affirmed by Dr. Gros 1 and others, but 

 having made no special observations on the subject, 

 I purpose deferring its consideration till some more 

 suitable period. 



It might be deemed probable that, if heterogenetic 

 changes occurred at all in higher animals, they would 

 be most prone to take place in some of the fluid or 

 semi-fluid secretions ; or else in some of those tissue- 

 elements which are constantly bathed with albuminoid 

 fluids either on the external surface of the body, or on 

 some internal surfaces. And this is found to be the 

 case. No better, longer known, or more generally 

 neglected instance can be alluded to than the trans- 

 formation of milk-globules, under certain conditions, 

 into large Fungus-germs, which speedily vegetate into 

 a kind of Penicillivm. 



This remarkable transformation was described by 



1 ' Bullet, de la Soc. de Nat. de Moscou/ 1847. 





