536 THE BEGINNINGS OF LIFE. 



knowledge concerning the distribution of large germs 

 or ova throughout the atmosphere. The great pre- 

 valence of such forms of life is, however, easily 

 explicable in accordance with the possibility of their 

 origin by more or less rapid series of ascending deve- 

 lopments, or by processes of direct transformation of 

 vegetal vesicles. 



Thus it is, as Pritchard says ', a well-known fact that 

 some Rotifers ^are common wherever water has re- 

 mained for a little time without disturbance — in 

 cisterns, depressions in the gutters of houses, saucers 

 of flower-pots, and similar situations.' And again, in 

 a memoir published in 1865 ^On the Anatomy and 

 Physiology of Nematoids ^ I stated that ' an examina- 

 tion of tufts of moss from the roofs of houses or from, 

 old walls, as well as of specimens of the yellow lichen 

 {Farmelia parietina) from the same situations, has invari- 

 ably revealed to me three principal kinds of animal-occu- 

 pants — specimens of Rotifers, of peculiarly slow-moving 

 arachnidal Tardigrada, and two or tliree different kinds 

 of Anguillulid'^. Precisely the same varieties of animal 

 life are spoken of as existing in the tufts of moss 

 examined by Spallanzani, and also in those which were 

 experimented upon by Andral and Gavarret. More- 

 over, I have found specimens of lichen brought from 

 Sweden tenanted by just the same types.' Now those 

 who believe that such forms of life are produced only 

 from pre-existing eggs of similar forms, must find it 

 1 ' Infusoria,' p. 653. ^ 'PhUos, Trans,' 1866, p. 617. 



