282 THE BEGINNINGS OF LIFE. 



It seems undoubtedly true, therefore, that living 

 organisms do descend in moderate numbers from un- 

 known heights, with rain and snow ; though it seems 

 just as obvious that the air of ordinary localities, near 

 the surface of the earth, only contains a very limited 

 number of recognizable spores or germs of living things. 

 On this subject we have, in addition-, the valuable 

 testimony of Prof. Jeffries Wyman, who says ^ : — ' We 

 have carefully examined the dust deposited in attics, 

 also that floating in the air, collected on plates of 

 glass covered with glycerine, and have found in such 

 dust, in addition to the debris of animal and vegetable 

 tissues, which last were by far in the greatest abun- 

 dance, the spores of Cryptogams, som.e closely resem- 

 bling those of confervoid plants ; and with them, but 

 much less frequently, what appeared to be the eggs of 

 some of the invertebrate animals, though we were un- 

 able to identify them with those of any particular 

 species. We have also found grains of starch in both 

 kinds of dust examined, to the presence of which 



Nees sur la grele rouge et sur une espece de pline rouge (loc. cit., t. i. 

 P- 573) rendent plus probable que, comme I'admettait aussi Wrangel 

 (Ibid. p. 35 1), cette Algue se forme dans I'atmosphere, que c est pas conse- 

 quent un aerophyte et qu'elle se produit, dans les temps d'orages et de 

 meteores ignes.' And elsewhere (p. 24) he says : — ' Zimmermann (" Archiv. 

 fiir die gesam. Naturlehre," t. i. p. :^57) a trouve dans de I'eau m^teorique 

 une substance organique particuliere differente du mucus et de I'extractif, 

 et qui degageait de I'ammoniaque en se d^composant ; cette substance, 

 appelee par lui pyrrhine, y etait melee avec du fer, du manganese, de la 

 chaux, de la magnesie, et de I'acide hydrochlorique.' 

 ^ * American Journal of Science,' July, 1862, 



