28 INFUSORIA AND RIIIZOPODA. ^«§> 13, 14. 



§13. 



If the vesicular cavities containing the liquid and colorless food of the 

 Stomatoda be examined under the microscope by a horizontal central inci- 

 sion, their contents appear colorless; but by changing the focus, viewing 

 alternately the convex and concave surfaces of the vesicle, the points of 

 junction between the colorless globules and the parenchyma appear colored 

 pale-red. This appearance, due to an optical illusion, might easily deceive 

 one into the opinion that the vesicles which are really colorless are colored. 



From this it is probable that Ehrenberg has described Bursaria vernalis 

 and Trachelms meleagris as having a red gastric juice. '^* 



The violet points which are found upon the back and neck of Nassula 

 elegans and Chilodon m-natus are only collections of pigment granules, 

 which, in the first case, are often absent, and in the second are often par- 

 tially dissolved. 



This last violet liquid has been regarded by Ehrenberg^-^ as a gastric 

 juice resembling bile. 



§ 14. 



The solid particles of food, whether surrounded by the parenchyma or 

 enclosed in a liquid vesicle, are moved hither and thither in the gelatinous 

 tissue of the body, during the contracting and expanding movements of the 

 animal. In some, the parenchyma with its contained food moves in a reg- 

 ularly circular manner, like the liquid contained in the articulated tubes of 

 Chara."' In Loxodes bursaria ^-' this circulation is remarkable, and of much 

 physiological interest. Its cause is yet quite unknown, for in no case is it 

 due to cilia, and it may be observed in individuals entirely at rest. Ehren- 

 berg/'^ therefore, is incorrect in regarding it as due solely to a contratile 

 power of the parenchyma, displacing the molecules. Much less is his ex- 

 planation '^* satisfactory, since the digestive tube of an infusorium can be 

 extended at the expense of its stomachal pouches, so as to fill the whole 

 body, giving it the appearance of having a circulation of molecules through- 

 out its entire extent. 



i"Die InfusionsUiierchen," pp. 321, 326, 329. 1836, p. 786; also Meyen, MiMer's Arch. 1839, 



Ehrenberg )ias, raoreovei-, in Tracheiius vielea- p. 75. 



g-rjs, confounded the contraclile cavities with those " Focke loc. cit.; also Erdl, MuUer''s Arch. 1841, 



non-conlractile, and which receive the food. p. 278. 



" Abhandl. d. Berliner Akad. 1833, p. 179 ; also s Loc. cit. p. 262. 



" Die Infusionsthierchen," pp. 319, 338, 339.* 4 MiiUer^s Archiv. 1839, p. 81. 



1 f^aginicola and Vorticclla. See Focke, Isis, 



Diatomacea;, portions of Algae or Desmidieae, and those of any animalcule with which we are ac 



with fragments of variously colored cotton, woolen, quainted. — Ed. 



and linen fibres, will give a picture of the animal ; * [§ 13, note 2.] In this connection should be 



to complete which, it is only necessary to add a noticed the experiments of Will (MUller^s Arch, 



few loose strings to the bag to represent the varia- 1848, p. 509). He found evidences of a biliary ap- 



ble radiant processes which it possesses around the paratus, with Vorticella, Epistijlis, and Bursaria. 



mouth." This animal, which is often found with These evidences are based on chemical reaction, 



bits of cotton protruding from its mouth, assumes and he describes no anatomical apparatus. I men- 



the most bizarre shapes. They appear to multi- tion this fact here, although Forticella belongs 



ply by fissuration and gemmation even when filled truly to the Bryozoa, and Bursaria to the Plana- 



with these heterogeneous particles, and, on the ria. — Ed. 

 whole, present characteristics as remarkable , as 



