50 THOUGHTS ON ANIMALCULES. 



cules have been exemplified. The digestive organs 

 consist of a series of globular stomachs, connected by a 

 common tube, which allows entrance to the food, and 

 exit to the effete particles. The food is brought to the 

 mouth by the currents produced in the water by the 

 cilia ; aeration is performed by the agency of the same 

 organs ; and the increase of the species is effected by 

 spontaneous division, each part, like the severed por- 

 tions of the polype, quickly growing into a perfect in- 

 dividual. Some are fixed to one spot in youth, but 

 become free when arrived at maturity, and are thus 

 capable of transporting themselves through the water 

 to localities possessing the conditions required by their 

 organisation. 



There are proofs of a muscular system, however sim- 

 ple, in the motions of the cilia, and in the rapid con- 

 tractions and changes of form which are exhibited in 

 certain species. No definite nervous system has been 

 detected, but there can be no doubt that a nervous in- 

 fluence is diffused through their structures; and the 

 existence of an eye-speck, or visual point, however 

 rudimentary, denotes a distinct nervous centre*. Eyes 



* " There must, therefore, be nerves or conductors of that influence for 

 the various movements, whether we consider them as voluntary, or re- 

 flex, that is, induced by stimuli, either within or without the body, upon 

 the contractile fibre." Professor Owen. 



