Poll/gastric htfusoria. 189 



On the 20th No. 1. had propagated five individuals by transverse 

 spontaneous division : in No. 4. eight individuals had in like manner 

 been generated. 



On the 21st no change had taken place. 



On the 22d there w^ere six nearly equal-sized individuals in No. 1., 

 and eighteen individuals in No. 4. 



On the 23d, the individuals were too numerous to be counted. 



Thus it was demonstrated that this species of Polygastrian would 

 continue for six days without any diminution of reproductive force, and 

 that on one day a single individual twice divided, and one of its divi- 

 sions effected a third fission. 



A similar experiment on a l^tylomicMa Mytilv?, an animalcule one- 

 tenth of a line in length, was attended with nearly the same results ; it 

 was supplied with the green nutrient matter, consisting of the Monas 

 pnlvnctdifs, and on the fifth day the individuals generated by successive 

 divisions were too numerous to be counted. 



And now you may be disposed to ask : To what end is this discourse 

 on the anatomy of beings too minute for ordinary vision, and of whose 

 very existence we should be ignorant unless it were revealed to us by a 

 powerful microscope } What part in nature can sucli apparently insig- 

 nificant animalcules play, that can in any way interest us in their orga- 

 nisation, or repay us for the pains of acquiring a knowledge of it.'' I 

 shall endeavour briefly to answer these questions. Tlie Polygastric In- 

 fusoria, notwithstanding their extreme minuteness, take a great share 

 in important offices of the economy of nature, on which our own well- 

 being more or less immediately depends. 



Consider their incredible numbers, their universal distribution, their 

 insatiable voracity ; and that it is the particles of decaying vegetable 

 and animal bodies which they are appointed to devour and assimilate. 



Surely we must in some degree be indebted to those ever active invi- 

 sible scavengers for the salubrity of our atmosphere. Nor is this all : 

 they perform a still more important office, in preventing the gradual 

 diminution of the present amount of organised maimer upon the earth. 

 For when this matter is dissolved or suspended in water, in that state 

 of comminution and decay which immediately precedes its final decom- 

 position into the elementary gases, and its consequent return from the 

 organic to the inorganic world, these wakeful members of natiu'c's invi- 

 sible police are everywhere ready to arrest the fugitive organised par- 

 ticles, and turn them back into the ascending stream of animal life. 

 Having converted the dead and decomposing particles into their own 

 living tissues, they themselves become the food of larger Infusoria, as 

 the Rotifa-a, and of numerous other small animals, which in their turn 

 are devoured by larger animals, as fishes ; and thus a pabulum, fit for 

 the nourishment of the highest organised beings, is brought back by a 

 short route, from the extremity of the realms of organic matter. 



There is no elementary and self-subsistent organic matter, as BufFon 



