INFUSORIA. 871 
I, Potyrr Tustrert,—Tentaculated polypi, united in a cominon fleshy 
body, destitute of solid internal axis, and covered with tubiform cylindery 
III Poryrr Vacinatt.— Tentaculated polypi, constantly fixed in an or- 
ganic covering, and forming, in general, compound animals. 
IV. Poryrr Denupati.—Tentaculated polypi, not forming a common 
envelope, fixed either constantly or spontaneously. 
V. Potyrr Crtiati.— Polypi destitute of tentacula, but with vibratile 
cilia, at or near the mouth. 
The habitations of the polypi, or the common masses formed by their 
united labors, are more or less calcareous or stony, from the madrepores, of 
a substance as consistent as shells, to the fibrous or membranous horny 
envelope of the sponge. Between these extremes are found every variety 
of consolidation and consistence ; but all are formed by animals approach- 
ing to one another in their general organization. Polypi are reproduced by 
ova or a separation of parts, natural or accidental. Their food is chiefly 
animal, derived, in the case of the smaller species, from the infusory ani- 
malcule which inhabit the waters. 
CLASS XIV.—INFUSORIA. 
Microscopic animals, gelatinous, transparent, polymorphous, and contractile ; 
no distinct mouth, nor constant or determinable interior organ; gencration 
Jissiparous or gemmiparous. 
Tue Infusory Animals, or those animalcules which have been observed in 
infusions of different plants, or in waters, more or less corrupted, and which are 
generally so minute as to require the aid of the microscope to discover them, 
form the last series of beings in the animal scale. The greater portion of 
these appear to have a gelatinous body, of extreme simplicity ; but syste- 
matical writers have, also, arranged in this class, many animals much more 
complicated in appearance, and which resemble them only in their extreme 
minuteness. Of animals so minute, the organization is but imperfectly 
known. Destitute of a distinct mouth, and internal organ of digestion, they 
seem to receive nourishment by absorption in all parts of their body. They 
are, however, capable of contraction and voluntary motion, and their repro- 
duction is effected by a separation of parts. Lewenhoeck and Muller first 
introduced these animals to the notice of naturalists, under the name of 
Infusoria. In Lamarck’s system, they compose the first class of his Inver- 
tebral Animals; Dumeril arranges them as the fourth family of his Zoophy- 
tes; and Cuvier makes them the fifth class of Zoophytes or those animals 
