§§ 9, 10. INFUSORIA AND KHIZOPODA. 25 



tical action of the water. <^* But with others the locomotive oro;an is a lone 

 retractile proboscis. '^^ With the Oxy trichina and Euplota, there are 

 fleshy movable points (uncini) upon the ventral surface, by which these 

 animals move about as upon feet. During these movements with the Oxy- 

 trichina, the posterior portion of the body is supported by many setose 

 and styloid processes, which point backward. 



The singularly varied and branching locomotive organs of the Rhizo- 

 poda are short, and digitated with Amasba, Diffiugia and Arcellay'' But in 

 the other genera they are elongated and filamentous.'"' 



CHAPTERS III. AND IV., 



NERVOUS SYSTEM AND ORGANS OF SENSE. 



§9. 



Although the Infusoria clearly evince in their actions the existence of 

 sensation and volition, and appear susceptible of sensitive impressions, yet 

 no nervous tissue whatever has as yet been found in them. If Ehren- 

 berg supposed the Polygastric Infusoria to possess a nervous system, he 

 did so because, having decided that the red pigment points of these ani- 

 mals were eyes, he inferred that they necessarily had a nervous ganglion 

 at their base. 



§10. 



With the naked Infusoria the sense of touch exists, undoubtedly, over 

 the whole body. But beside this, it appears specially developed, in many 

 species, in the long cilia forming vibratile circles, or in those movable 

 foot-like and snout-like prolongations of the body. In the same manner, 

 it is probable they have the sense of taste also ; for they seem to exercise 

 a choice in their food, although no gustatory organ has yet been found. 



All species, whether they have red pigment points or not, seem afi"ected by 

 light.. Without doubt, therefore, their vision consists simply in discrimi- 

 nating light from darkness, which is accomplished by the general surface of 

 the body, and without the aid of a special optical organ. 



The simple pigment point of many Infusoria,*^' and which jE/ire?2^er^ has 

 generally regarded as an eye,*-- has no cornea, and contains no body capa- 

 ble of refracting light ; there is, moreover, connected with it no nervous 

 substance. 



Ehrenberg attaches here too great an importance to the red color of the 



3 Amblyophis, Eii^lena and Peridinium, have Sc. Nat. Zool. IV. 1835, p. 343, pi. IX. ; also, V. 



a simple tlagelliform cilium, but with Chlorogo- 1836, p. 196, pi. IX. fig. A. See, also, his Ilistoire 



niiim it is double. des Infusoires, 1841, p. 249. pi. I. fig. 14-17 ; pi. 



* Tracke/ius trichophorus feels about with a II. fig. 1, 2, 7 — 10 ; pi. IV. fig. 1); Geoponus stel- 



long snout of this kind, without, however, produc- la borealis, Ifonioyiina germanica, according to 



ing a vortical action on the water. Khrenberg. Abhand. d. Berliner Akad. 1839, 



= See Ehrenberg, " Die Infusionsthierchen," p. 106, Taf. I. II. 

 Taf. A'lII. and IX. i Amb/yophis, Euglena, Chlorosonium, (fC. 



6 Gromia JluviatUis, Miliola vulgaris, Vor- 2 Abliandl. d. Berliner Akad. 1831, p. 12 ; also, 



ticialis strigilata, Euglypha tuberculosa, Tri- " Die Infusionsthierchen," p. 491. 

 nema acinus, according to Dujardin (Ann. des 



3 



