290 THE BEGINNINGS OF LIFE. 



met with in infusions after five or six days, could have 

 been derived from the multiplication of a few solitary 

 individuals, even by the combined methods of fission, 

 budding, and the so-called sexual reproduction. 



It is often stated that Ciliated Infusoria multiply 

 very rapidly by means of fission. But even towards 

 the close of the last century Gleichen 1 declared that 

 during the fifteen years in which he had been continually 

 watching these animals, he had only observed a process 

 of fission occur three times; and it was only after 

 some years of observation that De Blainville 2 was 

 actually able to satisfy himself that such a mode of 

 division might take place. He subsequently saw it 

 occur occasionally in certain specimens belonging to 

 the genus Kolpoda. Of late years, also, similar testi- 

 mony has been given on this subject. Mantegazza de- 

 clares that he has only seen ciliated Infusoria undergo 

 such a process of division two or three times, though 

 millions of these animals of different species had passed 

 under his observation during a space of fourteen 

 months ; while M. Pouchet, during observations extend- 

 ing over many years, says he has never once seen a 

 Paramectum divide. Specimens of Kolpoda he has how- 

 ever more frequently found presenting appearances sug- 

 gestive of fission. But with regard to the Vortnell<e^ 

 which, since the times of Spallanzani, have been de- 

 scribed as particularly prone to undergo such a division, 



1 ' Dissert, sur la Generation, &c.' 



2 'Diet, des Sc. Nat.' torn. Ix. p. 1^4. 



