1872.] 



Modes of Origin of Infusoria fyc. 



249 



which had again become less refractive, distinctly separated from the 

 cyst- wall *. 



As the virtues of this infusion seemed to be getting exhausted, on the 

 same (tenth) day I transferred a portion of the pellicle to the surface of a 

 new weak infusion of hay, which had been previously boiled. On the fol- 

 lowing day the Monads were found to have increased very much in size, 

 and so also had many of the Amoebae. Several large ovoid Monads on 

 measurement were found to be as much as T in length ; they had, in 

 fact, become nearly twice as long as the largest of those which had existed 

 in the old infusion. 



Five days afterwards (sixteenth day), when another portion of this 

 transferred pellicle was examined, all the Monads were found to have dis- 

 appeared, with the exception of a few which were in a motionless state, and 

 were apparently about to be converted into Amoebae. These latter organ- 

 isms existed in teeming myriads : a portion of them had become encysted, 

 whilst of the rest about one half were active, and the others, though not 

 encysted, were almost motionless and more or less granular. On further 

 examination, it was found that the granular Amoebae (fig. 3, i-m) were 

 organisms in a dying state, and that the contained particles were new living 

 units which gradually developed into Bacteria. All the stages of this 

 development were to be seen. Thus there were a considerable number of 

 languid Amoebae which merely displayed a slight increase in the customary 

 number of minute particles situated near or around the nucleus. There were 

 others in which these minute granules, were more numerous ; and others 

 still, quite motionless and spherical, which were densely packed with minute 

 particles throughout their whole substance — these particles being mo- 

 tionless and less than yoSoTTO"" m diameter. In many of such Amoebae a clear 

 vacuole was still to be seen. In other organisms the particles had become very 

 slightly larger, whilst the protoplasmic substance in which they had been 

 produced had become fluid, and the particles were to be seen in active 

 movement within the attenuated film constituting the outer layer of the 

 old organism whose nucleus was still visible. When reduced to this con- 

 dition, trembling movements of the whole mass were seen, owing to the 

 resultant agitations produced by the contained units. Soon the attenuated 

 outer membrane gave way, and, when the contained units were liberated, 

 they at once exhibited very active movements of progression, after the 

 fashion of minute Bacteria. The surrounding fluid was, in fact, crowded 

 with similarly minute and active B act etna, and with others slightly larger, 

 which had evidently been produced in this manner. 



Such was the fate that overtook those Amoebae which lived latest in the 



* In the course of the next few days myriads of the Amoeba? had undergone this 

 kind of change, which seems to follow quite naturally as soon as the activity of their 

 vital processes becomes diminished. It is the extraordinary molecular activity and 

 constant change of shape of the Amoeba which tends to prevent the earlier occurrence 

 of this primary differentiation. 



