CONCLUSION. 337 



than that of a whafe ; and one of the last conclusions at 

 which we arrive, is a conviction that the greatest and most 



probable explanalion, and the case of Infusoria no longer appears to dif- 

 fer from that of other animals as to the principle on which their propaga- 

 tion is conducted. Tiic chief peculiarity seems to consist in this, that 

 their increase takes place both by the oviparous and viviparous manner 

 of descent from parent animals, and also by division of the bodies of indi- 

 viduals. 



Tlie great difficulty is, to explain the manner in which the eggs or bodies 

 of preceding individuals can find access to each particular infusion. This 

 explanation is facilitated by the analogous cases of various fungi which start 

 into life, without any apparent cause, wherever decaying vegetable matter is 

 exposed to certain conditions of temperature, humidity, and medium. Fries 

 explains the sudden production of these plants, by supposing the light and 

 almost invisible sporules of preceding plants, of which he has counted above 

 10,000,000 in a single individual, to be continually floating in the air, and 

 falling every where. The greater part of these never germinate, from not 

 falling on a proper matrix; those which find such matrix start rapidly into 

 Jife, and begin to propagate. 



A similar explanalion seems applicable to the case of Infusoria ; tlie ex- 

 treme minuteness of the eggs and bodies of these animalcules probably allows 

 them to float in the air, like the invisible sporules of fungi ; they may be 

 raised from the surface of fluids by various causes of attraction, perhaps 

 «ver by ovaporation. From every pond or ditch that dries up in summer, 

 these desiccated eggs and bodies may be raised by every gust of wind, and 

 dissipated through the atmosphere like smoke, ready to start into life when 

 ever they fall into any medium admitting of their suscitation ; Ehrenherg- 

 has found them in fog, in rain, and snow. 



If the great aerial ocean which surrounds the earth be thus charged witli 

 the rudiments of life, floating continually amidst the atoms of dust we see 

 twinkling in a sunbeam, and ever ready to return to life as soon as they 

 find a matrix adapted to their development, we have in these conditions 

 of the very air we breathe a system of provisions for the almost infinite 

 dissemination of life throughout the fluids of the present Earth ; and 

 these provisions are in harmony with the crowded condition of the waters 

 of the ancient world, which is manifested by the multitudes of fossil mi- 

 croscopic remains, to which we have before alluded. (See Sect. viii. page 

 ->90.) 



Mr. Lonsdale has recently discovered tiiat the Chalk at Brighton, 



Gravesend, and near Cambridge, is crowded with microscopic shells; 



thousands of these may be extracted from a small lump, by scrubbing it 



with a nail brush in water ; among these he has recognised vast numbers 



VOL. I. — 29 



