ROTIFEEA, 43 



for a long time in a state of desiccated torpidity. I sliall presently 

 have to allude to the experiments of Spalanzani and others on the 

 wheel-animalcules, in illustration of this curious property. Some 

 who have repeated his experiments have not succeeded in reviving 

 the subjects after so long a period of inanimation as four years*; 

 nevertheless, great tenacity of life is unquestionably, notwithstanding 

 the delicate tissues of the Infusoria, a property of creatures of their 

 grade of organisation ; and what holds good of the parent, in regard to 

 this property of latent life, must, a fortiori, be allowed to the ovum 

 and encysted pupa. 



The supposed act of oviparous generation, that of sending forth 

 countless germs through the fatal laceration or dissolution of the 

 parent's body, is most commonly observed in the well-fed Polygastria, 

 which crowd together as their little ocean evaporates; and thus 

 each leaves, by the last act of its life, the means of perpetuating 

 and diffusing its species by thousands. When the once thickly ten- 

 anted pool is dried up, and its bottom converted into a layer of dust, 

 these inconceivably minute and light germs will be raised with the 

 dust by the first puff of wind, diffused through the atmosphere, and 

 may there remain long suspended ; forming, perhaps, their share of 

 the particles which we see flickering in the sunbeam, ready to fall 

 into any collection of water, beaten down by every summer shower 

 into the streams or pools which receive or may be formed by such 

 showers, and, by virtue of their tenacity of life, ready to develope 

 themselves wherever they may find the requisite conditions for their 

 existence. 



The possibility that such is the design of the alleged oviparous 

 and of the observed encysted multiparous generation of the Infu- 

 soria, and such the common mode of the diffusion of their germs, 

 renders the hypothesis of spontaneous generation, which has been 

 so frequently invoked to explain their origin in new formed natural 

 or artificial infusions, quite gratuitous. If generative organs might, 

 at first sight, seem superfluous in creatures propagating their 

 kind by gemmation and spontaneous fission, equivocal generation 

 is surely still less required to explain the origin of beings so 

 richly provided with the ordinary and recognised modes of multipli- 

 cation. Many experiments have, however, been detailed, in which 

 adequate precautions appeared to have been taken to prevent the 

 possibility of the entry of fertile germs into the fluid experimented 

 on, after means had been taken to destroy all that it might contain. 

 From these experiments, the mere access of atmospheric air, light, 



* CXXXV. vol. ii. p. 127. 



