396 MANIPULATION. 



are contained ; if they be vorticellEe or rotiferse, the particles of 

 colouring matter wUl show the vibratile actions of the cilia, 

 whilst other particles, when swallowed by the animacules, 

 will give a rich tint to the various compartments of their 

 alimentary canal. If the animalcule cage be a large one, a 

 very small quantity of the carmine may be rubbed upon one 

 part of the tablet, and the water containing the animalcules 

 being placed upon it may be mixed up with the carmine in 

 the usual manner. Of the three colours, the sap-green wiU be' 

 most easily swallowed by the insects, although the carmine 

 shows best in the water, whilst the indigo is not so easily 

 managed as the other two. The colours when employed 

 should be of the purest kinds, otherwise the animalcules will 

 not easily swallow them, or, if swallowed, the death of the 

 creature wUl speedily result. 



FOSSIL INFDSOBIA. 



An endless variety of Infusoria are met with in the fossil 

 state, the siliceous skeletons of which have become aggregated 

 together in such immense masses, that not only are vast 

 tracts of country and chains of mountains formed of them, 

 but even strata, several yards in thickness, upon which 

 cities are built. Amongst the first discovered of the infusorial 

 strata were the polishing slates of Bilin and Tripoli, then the 

 Berg-mehl or Mountain meal, of which almost the entire mass 

 is composed of the sUiceous skeletons of different species of 

 Navicula and Bacillaria. In more modern times, the Ameri- 

 can Continent has, through the researches of Professor Rogers, 

 furnished remarkable examples of infusorial sand-stone ; one 

 of these, at Richniond, in Virginia, is many miles in length, 

 and, in some places, as much as fifteen feet in thickness. The 

 great mass of chalk, as seen in the cliffs and rocks of our coasts, 

 is made up principally of minute foraminiferous shells ; the 

 flints also, which are so abundant in the chalk, are now gene- 

 rally considered to be composed of animal remains, and in 

 them may be found fish scales, bones, spicula of sponges, 

 Xanthidia, shells of various kinds, and numerous small 

 Zoophytes. 



