and its Nucleus in Cliara verticillata. 29 



side of it in which the nucleus is imbedded. That the vesicula, 

 when greatly distended, does render some of the Infusoria sphe- 

 rical, may easily be seen by the state in which Plasconia and 

 Vorticella burst from their cysts respectively when the vesicula 

 is expanded to the utmost to produce the rent, and then sub- 

 siding after the animalcule has effected its escape, thus allows of 

 its returning to its natural form ; and it is not unreasonable to 

 infer that the same thing takes place in Amoeba, to render its 

 plane form spherical, and vice versd^. Nor should we omit in 

 this analogy the vacuolation which takes place in the protoplasm 

 of Chara just before the cell dies, or when it is weakened by 

 disease or injury, which is a common occurrence in the vesicula 

 and its vacuolar system in Amoeba and other Infusoria under 

 similar circumstances. 



The most interesting point, however, which this analogy brings 

 forth is the correspondence between the rotatory motion of the 

 protoplasm in the cell of Chara, and that of the sarcode of Amoeba 

 and other Infusoria; since, by considering this motion in diflferent 

 organisms, we may perhaps arrive at some notion of the cause 

 by which it is produced in all. In the Planarise and Rotatoria, 

 the lash of cilia, which projects from the hepatic cells that line 

 the stomachs of these animalcules respectively, appears to rotate 

 the food during the process of digestion ; but in the second part 

 of the alimentary canal of the Rotatoria, where there are no he- 

 patic cells, the surface is seen, on the approach of anything into 

 it, to be covered with cilia. Again, in Vorticella and Paramecium 

 Aurelia, the digestive globules also are slowly circulated round 

 the abdominal cavity, if I may so term it, in the midst of the sar- 

 code or internal mucus ; and when we watch this circulation nar- 

 rowly, for instance, in the posterior part of Vaginicola crystallina 

 (Ehr.), we see that the bodies in which the chief motion exists 

 are very minute and apparently stationary, and that, while their 

 movements are very rapid, the circulation of the pellets of food 

 is very slow ; hence they would appear to be cilia. The same 

 kind of circulation occurs in Amoeba, but is so tardy, and this 

 Infusorium is so incessantly changing its shape, that it is not 

 seen, under ordinary circumstances. The movement of the 

 rotating protoplasm in the Characese is also very slow ; for, when 

 it is viewed in the long iuternodes of Nitella with a very low 

 power, or even with the naked eye, it seems hardly to move 

 faster than the foot of a Gasteropod ; still there is no positive 

 evidence that it moves round the cell after the manner of the 

 latter, although it would appear to possess the power of move- 

 ment per se. Hence the question remains undecided, viz. 

 whether it moves round the cell by itself, or by the aid of 

 * Idem. See remarks on this poiut, vol. xviii. p. 131. 



