VIEWS OF DTJJAKDIN AND MEYEN. 39 



larger size (and frequently irregular shape, its contour being lobulated), 

 evidently formed by the union of several smaller vacuoles, which, having 

 been successively brought into contact, have become fused together like 

 bubbles of gas. This large posterior vesicle becoming more and more 

 distended, its walls become thinner, and at last it opens externally by a 

 wide lateral fissure, discharging its contents and then contracting to a 

 comparatively small size. If this process be that which generally takes 

 place (as it is supposed to be by H. Dujardin), the excretory orifice will 

 be constantly formed at that point where the internal vesicles (so-called 

 stomachs) terminate their career after having passed through the glu- 

 tinous interior of the animalcule ; and in this case its position, although 

 it is not the termination of an intestinal canal, may be sufficiently con- 

 stant to afford a character of classification. 



(80.) The celebrated botanist, M. Meyen*, regards the true Infusoria 

 as being vesicular beings, having their interior filled with a kind of 

 mucous substance. The thickness of the walls of the body, according 

 to this observer, is in many species such as to be easily appreciated, and 

 contains a spiral structure, which is readily perceptible, and which, as 

 he thinks, establishes a complete analogy between these creatures and 

 vegetable cells. In the larger kinds of Infusoria a cylindrical canal (the 

 oasophagus) passes obliquely through the integument, and becomes dilated 

 inferiorly, when distended with nutritive matter, to the size of the coloured 

 globules met with in the interior of the body. The inner surface of this 

 oesophageal tube is lined with cilia, by the action of which alimentary 

 substances are kept in movement until they acquire a spherical shape. 

 When the pellet thus formed becomes as large as the size of the pharynx 

 will allow, it is expelled therefrom, and pushed into the cavity of the 

 animalcule ; a second pellet then accumulates, if any solid particles are 

 contained in the surrounding fluid, which being in like manner impelled 

 into the general cavity of the body, pushes the preceding one (which is 

 now surrounded with mucosity) before it, and so successive pellets are 

 formed one after the other, with which the cavity of the body becomes 

 filled, giving the appearance that induced Professor Ehrenberg to 

 consider these little beings as furnished with numerous stomachs. 

 If no solid particles exist in the fluid surrounding the animalcule, the 

 pellets are less consistent, exhibiting the appearance observable in 

 specimens living in colourless water, in which case they are made up of 

 a small number of particles, and seem to be principally composed of 

 mucosity. Sometimes (observes M. Meyen) two of the pellets so formed 

 are, when forcibly pressed together by the contraction of the body of the 

 animalcule, observed to coalesce and become united into one mass, a 

 circumstance in itself sufficient to prove that they are not enclosed in 

 stomachal walls. 



(81.) In order to witness the formation of the pellets above de- 

 * " Quelques Observations sur les Org. digest, deslnfus.," Ann. des Sc. Nat. 1839. 



