INFUSORIA. 



[ 341 ] 



INFUSORIA. 



Pathol. Anat. ; Bennett ; Edinh. Monthly 

 Journ. 1850. x. p. 150; W. Jones, Ghiy's Hosp. 

 Reports, 1850 ; Paget, Lectures on Inflam- 

 mation ; Gluge, Atlas d. Path. Anat. 



INFUSORIA. — An order of Animals. 



Char. Microscopic animals not furnished 

 with either vessels or nerves, but exhibiting 

 internal spherical cavities ; motion effected 

 by means of ciHa, or variable processes 

 formed of the substance of the body, true 

 feet being absent. 



(Body composed of proteine compounds; 

 soluble in solution of potash.) 



Every one who has examined with a micro- 

 scope a drop of water containing animal or 

 vegetable matter which has been set aside 

 for a time, or a drop from any pool or ditch, 

 must have observed numerous minute beings 

 in active motion, resembling some of those 

 figured in Pis. 23, 24 & 25 ; these are Infu- 

 soria, or the animalcules of infusions. 



Perhaps no question has been more dis- 

 cussed than that of the structure of the 

 Infusoria. Ehrenberg regards them as 

 being highly organized, and furnished with 

 distinct organs like the higher animals ; 

 whilst more recent authors consider them as 

 representing simply a nucleated cell. Unfor- 

 tunately the facts are not accordant with 

 either of these views; the question must at 

 present be considered as still sub jiidice. 



The structure of the Infusoria is not the 

 same in all the famihes. In the Amcebsea, 

 in which the simplest form of animal struc- 

 tm-e occm-s, the entire substance of the body 

 consists of a glutinous, homogeneous or 

 slightly granular diaphanous sarcodic mass 

 (PI. 23. fig. 9 a), in which no trace of organs 

 can be detected. In the substance of the 

 body a number of rounded moving spaces 

 are frequently visible, containing foreign 

 particles serving as food, and derived from 

 the surrounding water (fig. 9 b). The entrance 

 of these particles takes place, or has been 

 described to take place, in two ways ; either 

 by the tentacular expansions of the body 

 sun'ounding them, and forcing them towards 

 the interior, where they are digested whilst 

 surrounded by the inverted outer portion of 

 the body, or they are urged into the sub- 

 stance itself, just as a marble might be 

 forced into a mass of jelly or paste, and 

 being moved through the body by the 

 general contraction of its substance, are ulti- 

 mately expelled. In the next simplest 

 family, in the Ai-cellina, the sarcodic mass is 

 contained within a distinct envelope or cara- 

 l)ace, from an orifice in which the tentacular 



expansions are protruded (PI. 23. fig. 39 ; 

 PL 25. fig. 24). 



These two families have been separated 

 from the Infusoria by some authors (Rhizo- 

 poda) ; but the same structure exists in 

 many of those which are left by these 

 authors among the Infusoria. 



In other Infusoria the outer portions of 

 the body appear to be firmer than the inner; 

 hence these may be said to have an outer 

 coat. In others again, a fine pellicle invests 

 the surface, which is distinctly separable; 

 whilst in the last form, the body is more or 

 less enclosed in a carapace or shell, to which 

 it is to a greater or less extent attached. 

 We shall examine the fm-ther structure of 

 the Infusoria, by considering the parts in 

 order and separately, to prevent confusion. 



Integument. — The carapace must be viewed 

 as a secretion from the body of the animal, 

 and not as corresponding to an integument. 

 This structure has been noticed under 

 Carapace ; in Arcella it is undissolved 

 by potash, even on boiling; and it is not 

 coloured red by Millon's test, nor blue by 

 sulphuric acid and iodine ; hence it does not 

 appear to consist of either a proteine-com- 

 pound or cellulose ; perhaps it is composed 

 of chitine. 



In some Infusoria a distinct outer coat is 

 present, as in Paramecium. It often becomes 

 visible when the Infusoria are kept in a small 

 quantity of water upon a slide, the globules 

 of sarcode which escape from rupture of the 

 body carrying it before them. It is fre- 

 quently beautifully marked with minute 

 depressions (PI. 25. fig. 1), regularly arranged, 

 and from each of which a cilium arises. 

 Dujardin distinguishes a contractile and a 

 non-contractile integument; but in many 

 instances, this author does not distinguish 

 with sufficient clearness between the carapace 

 and the integument, and his non-contractile 

 integument frequently corresponds to the 

 carapace. Beneath the outer coat, the 

 substance of the body frequently appears 

 thicker, although no distinct layer can be 

 separated; and it is doubtful whether the 

 markings are situated in the outer coat, or 

 whether the latter derives them from being 

 moulded upon the inner coat, to which they 

 properly belong. The stmctures here exhibit 

 some analogy with those of the cell-contents 

 of the cells of certain Confervoid Algse. The 

 outer pellicle may correspond to the primor- 

 dial utricle or external mucilaginous layer. 

 The next coat, when distinguishable, is not 

 so well defined ; it is strictlv bounded on the 



