on the motions of Infusoria. 349 



again accumulated at one side of the surface of the water, and 

 as it happened both times to be the side next the window where 

 they were collected, I suspected that, like the Hydrce, they might 

 have been attracted to that side by the influence of the light. 

 I now removed the vessel to the opposite side of the window, 

 that the light might reach it by a different direction, and in about 

 an hour I found that they had again collected precisely on the 

 part of the margin nearest to the light. The vessel was after- 

 wards placed at various distances from the window, and in vari- 

 ous directions with regard to it, and in more than twenty suc- 

 cessive trials, I found the animalcules invariably betake them- 

 selves to the most illuminated point of the margin. On turn- 

 ing the vessel gently round from the window, I could observe 

 the animalcules with a pocket lens bound forward almost in a 

 straight line to the light, after slowly detaching themselves 

 from the side where they had previously accumulated. When 

 they are swimming dispersed through the water, they seem to 

 have disappeared, being almost invisible to the naked eye 

 when thus separated, and exhibiting an intense green colour 

 only when collected closely together. 



The presence of eyes in such animals has been ridiculed by 

 later naturalists, as implying the existence of an optic nerve, 

 a centre of nervous energy, and a general complicated organi- 

 zation, which are contradicted by microscopic inspection. The 

 motions of Infusoria are by many believed to be automatic, 

 and Lamarck conceives them to result merely from the action 

 of various imponderable fluids pervading all bodies. Distinct 

 organs of vision belong only to those animals which require 

 to modify the light, so as to produce images of distant objects, 

 to enable them to shun their foes, to select their proper food, 

 or to provide for the continuance of their race, and are not 

 met with in the Infusoria, Zoophyta, or Radiata. It is inte- 

 resting, however, to observe, that an agent so extensively dif- 

 fused over nature as light has an obvious and powerful influ- 

 ence on the motions of the Furcocerca viridis, an animalcule 

 which exhibits nearly the simplest known form of animal orga- / 

 nization. — — ' 



