708 



KADIATA; 



of the Rroup will ha.e to undergo a similar transference ; but it would oe premature to attempt the 

 separation at present. 



The forms presented by these Animalcules are extremely various. In some «'e can scarcely detect 

 any definue shape; their bodies appear composed of a mass of gelatinous matter destitute of any 

 sohd support, which may project itself into almost any figure. In others there is still a considerable 



variety in the forras assumed by the same 

 individual under different circumstances (Fig, 

 626, d) ; but still a prevailing shape can be re- 

 cognized. In others, again, thebody, although 

 r^>^ ytill unprotected by any firm envelope, appears 

 to undergo little change in figure, except wheu 

 affected by temporary pressure. But there are 

 many species which cannot be influeaced even 

 by this; their soft bodies being enclosed in a 

 delicale but firm integument, strengthened by 

 a deposit of siliceous matter. These are termed 

 Fig. 22.— Varioits FoRM.s or Ai^iMALrcLRs. loricaied Infusoria; and their envelopes are 



often preserved after the death uC the Animalcules, accumulating by their multiplication into vast 

 masses. lo these luricated tribes, however, were included many forms now transferred to the Vege- 

 table kingdom. 



Those seem most entitled to the designation Animalcules^ which have a distinct mouthy surrounded 

 by vibratile cilia. By the ageni-y ot cnese cilia, food is taken into the cavity of the body ; and refuse 

 matter is sometimes expelled through ^separate orifice. When these Animalcules have been allowed 

 CO remain for a short time in water, in which finely-divided particles of colouring matter are sus- 

 pended, the whole of the transparent body is seen to be studded with coloured globules of a tolerably 

 uniform size, each of them composed of an aggregation of particles. 



From this class of facts it has been inferred by Professor Ehrenherg that a larg<^ number of globular 

 cavities exist in the substance of the body, into which the food is received; ano he considers that 

 these all sometimes communicate directly with the mouth ; but that in general they are arranged 

 along an intestinal tube, into which they open by a short neck. Notwithstanding the high authority, 

 however, which Prof, E. has acquired from his patient and long-continued study of these Animalcules, 

 this doctrine has not received very general assent from those mosi competent to judge of its mprit.^, 

 being regarded as rather an hypothesis founded on observations, than a? itself entitled to rajik as 

 an observed fact. 



It is to the action of the vibratile cilia, also, that tlie crreat variety of movements exhibited by these 

 beings is entirely due ; and tliis fact would seem to mdicate that these movements are not directed by 

 consciousness. No organs of sensation have been shown to exist in tliis class of Animalcules ; nor 

 has any indication of a nervous system been discovered. 



Several modes of propagation are seen in this class of Animalcules. Not nnfrequently we observe 

 a reproduction by the development of gcmm<s or liuds, as in the Vorticella (Fig. -2, a) ; bat in other 

 species the multiplication is ertected h_\' thi:' separation <\\ the body into two parts, the ili\i-ion some- 

 times tnking place longitudinally, as at h-, sometimes transversely, as at c. This process takes place 

 with such rapidity under favourable circumstances, that it has been calculated that from a single Pa- 

 ramcecium (Fig. 22, e), no fewer than 268,000,000 might be produced in a month. In other tribes, 

 however, propagation takes place by ova or germs evolved within the body of the parent, the greater 

 part of whose bulk is often made up of them. 



When the gemmfe remain adherent, instead of becoming detached, compound structures are pro- 

 duced, more or less resembling those of Zoophytes in miniature. The groups of Vorticella are 

 examples of this; but a still more remarkable instance is the Yoivox, formerly designated the globe- 

 animalcule.^ but now known to be composed of a congeries of Monads produced by gemmation from a 

 single individual, and invested by a common envelope. 



The classification of this group proposed by Ehrenherg is principally founded on the various forms 

 under which he believes the alimentary canal to exist in them ; and until the existence of these ehaU 

 be generally admitted, the classification cannut be regarded as having any permanent value. 



