80 THOUGHTS ON ANIMALCULES. 



the food upon the little block or anvil beneath, (pi. xii, 

 fig. 1, , and p, 55, lign. 5, fig. 2). This creature has 

 one eye, which is .quadrangular, a respiratory tube, 

 and trembling organs (branchice) in the interior. It is 

 oviparous, and the eggs are attached to the body till 

 the young are hatched. 



II. BAKER'S BRACHIONUS, (B. Bakeri, pi. xii, fig. 2). 

 The shell of the other species is scabrous or rough, 

 with six unequal spines on the upper, and two very 

 long lateral ones on the lower end ; its jaws are shewn 

 in p. 55, fig. 2, a. 



These minute beings aggregate together in number- 

 less myriads, so as to form whitish masses that float in 

 the water; after the death of the animals the shells 

 retain their form, and accumulate in layers at the 

 bottom of pools, lakes, &c. 



STRATA OF LIME AND FLINT FORMED BY INFUSORIA. 

 In many families of the polygastric Infusoria, the 

 cases, or shells, consist either of lime, silex (flint), or 

 iron ; and these retain their form and structure for un- 

 limited periods of tune. From the inconceivable num- 

 bers of these shell-animalcules which swarm in every 

 body of water, whether fresh or salt, and the immense 

 rapidity with which the species increase by spon- 



