CONCLUSION. 
447 
the last conclusions at which we arrive, is a 
Conviction that the greatest and most important 
operations of nature are conducted by the agency 
of atoms too minute to be either perceptible by 
^he human eye, or comprehensible by the hu- 
understanding. 
We cannot better conclude this brief outline 
of the history of fossil Poly paries, extending as 
*^^cy do, from the most early transition rocks to 
present seas, than in the words wdth which 
These most curious observations throw important light on the 
'^*^scure and long-disputed question of equivocal generation ; the 
^®ll-known fact that animalcules of definite characters appear in 
"’fusions of vegetable and animal matter, even when prepared 
"'’fh distilled water, receives a probable explanation, and the case 
Infusoria no longer appears to dilfer from that of other animals 
fo the principle on which their propagation is conducted. The 
"hief peculiarity seems to consist in this, that their increase takes 
f*bce both by the oviparous and viviparous manner of descent from 
f^rent animals, and also by division of the bodies of individuals. 
The great difficulty is, to explain the manner in which the eggs 
bodies of preceding individuals can find access to each parti- 
"ular infusion. This explanation is facilitated by the analogous 
'^^ses of various fungi which start into life, without any apparent 
wherever decaying vegetable matter is exposed to certain 
'^""ditions of temperature, humidity, and medium. Fries explains 
sudden production of these plants, by supposing the light and 
"luiost invisible sporules of preceding plants, of which he has 
""Unted above 10,000,000 in a single individual, to be continu- 
ally floating in the air, and falling every where. The greater 
of these never germinate, from not falling on a proper matrix ; 
f’ose which find such matrix start rapidly into life, and begin 
fo propagate. 
A similar explanation seems applicable to the case of Infusoria ; 
’^"0 extreme minuteness of the eggs and bodies of these animal- 
