LEEUWENHOEK 217 



of Volvox, Hsematococcus and Polytoma. It is again 

 Leeuwenhoek who starts the literature of the ciliate 

 Infusorians by his descriptions of organisms found in 

 rain -water and pepper-infusions, of species parasitic upon 

 the frog, and of Yorticellid colonies. He remarked that 

 no Infusorians could be found in fresh rain-water col- 

 lected by a leaden gutter, but that they appeared in the 

 course of a few days. 



Volvox ^ 



In water from a ditch Leeuwenhoek remarked a 

 number of green spheres, which moved slowly about, 

 rotating as they moved. Closer examination showed 

 that each sphere was composed of a multitude of par- 

 ticles beset with small protuberances. Several small 

 spheres might often be seen within a single large one, 

 and Leeuwenhoek was fortunate enough to see them 

 escape one by one through an opening in the parent 

 sphere, until none remained behind ; as soon as they 

 became free they began to swim about ; he detected the 

 germs of a third generation within the daughter-spheres. 

 The small spheres grew rapidly after liberation. Not- 

 withstanding its power of locomotion, the mode of pro- 

 pagation led Leeuwenhoek to decide that Volvox was 

 more like a plant than an animal. 



Henry Baker in 1753 showed that the protuberances 

 which Leeuwenhoek had seen on the green particles of 

 Volvox bore " short moveable Hairs or Bristles " (pairs 

 of cilia), and that these set up the movements of the 

 spheres. The name of Volvox was given by Linnaeus 

 (1758). 



lEpist. 122, Ep. 8oc. R. (1700). 



it 



