20 ZOOLOGY. 
mouth to the vent, which he regards as so many stomachs. This view 
passed undisputed for a considerable time; for although other observers 
failed to detect the connexion between the supposed stomachs and intestine, 
the failure was attributed to want of skill in microscopic manipulation. 
Ultimately this structure was doubted, although Pouchet reaffirmed it in 
1848, and among others, Professor Rymer Jones expresses his doubts as 
follows : 
‘In carnivorous animalcules which devour other species, we might expect, 
were these the stomachs, that the prey would at once be conveyed into one 
or other of these cavities ; yet, setting aside the difficulty which must mani- 
festly occur in lodging large animalcules in these microscopic sacs, and 
having recourse to the result of actual experience, we have never in asingle 
instance seen an animalcule, when swallowed, placed in such a position, but 
have repeatedly traced the prey into what seemed a cavity excavated in the 
general parenchyma of the body. 
‘‘Tn the second place, the sacculi have no appearance of being peduncu- 
lated, and consequently in a certain degree fixed in definite positions. 
So far from their having any appearance of connexion with a central canal, 
they are in continual circulation, moving slowly upwards along one side of 
the body, and in the opposite direction down the other, changing, moreover, 
their relative positions with each other, and resembling in every respect the 
colored granules visible in the gelatinous parenchyma of the hydra. 
‘“‘'With respect to the central canal, we have not in any instance been 
able to detect it . . . much less the branches represented as leading from it — 
to the vesicles or stomachs, as they are called. Even the circumstances 
attending the prehension of food would lead us to imagine a different 
structure ; witness, for example, the changes of form which Hnchelis pupa 
undergoes when taking prey almost equal to itself in bulk. Such a capability 
of taking in and digesting a prey so disproportionate, would, in itself, go far 
to prove that the minute sacculi were not stomachs; as it.evidently cannot 
be in one of these that digestion is accomplished.”—General Outline of the 
Animal Kingdom, 1841. 
The observations of Dujardin (Hist. nat. des Zooph. Infusoires, 1841) 
confirm those of Jones. He thinks that they do not lay eggs. 
Many of Ehrenberg’s discoveries were made by infusing indigo or carmine 
in the water in which he kept Infusoria, and this being swallowed, marked 
the limits of the internal cavity. He did not detect the liver, spleen, or 
organs of circulation and respiration ; but there are two organs in the gullet 
supposed to be analogous to salivary glands. 
All Infusoria live in the water, some being confined to fresh, and others 
to salt water; but there are others which inhabit both. Some swim about 
almost continually, some attach themselves at will to plants or animals, and 
others are attached to particular animals, as to the Cyclops or waterflea, the 
freshwater Polypus ; and even upon or within other Infusoria. One species 
is found in the rectum of frogs, and another (Paramecium compressum) m 
the intestines of the earthworm. Agassiz has observed the eggs of Planarva 
producing a species of “ Paramecium” which was consequently an immature 
condition of that animal. All the attempts of Ehrenberg to detect Infusoria 
as inhabitants of the air have failed. 
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