86 THOUGHTS ON ANIMALCULES. 



Infusoria always appear in vegetable infusions, simply 

 because their ova or germs, being everywhere present, 

 find in such fluids a proper medium for their develop- 

 ment : hence the same kinds of infusions do not always 

 contain the same species of animalcules. 



The atmosphere, which is always charged with in- 

 finitesimal particles of matter, both organic and inor- 

 ganic, wafts in every breeze immense quantities of the 

 sporules of plants*, and of the ova of animalcules. 

 The rapid increase of the Infusoria yields a never- 

 failing supply of their germs, and countless myriads are, 

 therefore, everywhere ready to burst into life, and go 

 through their assigned phases of development, when 

 placed under the conditions specially required by the 

 type of organisation to which they belong f. 



* The sporules of some Fungi are so minute, and occur in such im- 

 mense numbers, that in a single individual (of Reticularia) more than ten 

 millions have been counted ; and they are so light and subtle, that they 

 are dispersed by the slightest agitation of the air, and even by evapora- 

 tion. The germs of these minute and simple forms of vegetation must, 

 therefore, always be present in the atmosphere. 



t The Acari observed by Mr. Cross in the fluids of his galvanic ap- 

 paratus, cannot justly be regarded as offering a valid objection to this ex- 

 planation of the phenomenon. The appearance of these Acari, notwith- 

 standing the precautions employed to exclude or destroy their ova, in the 

 experiments of Mr. Cross and Mr. Weekes, does not present the same dif- 

 ficulty as the occurrence of Entozoa in the chambers of the human eye, 

 &c. See Appendix, 



