662 



MICROSCOPE. 



pbere is teeming with minute germs of animal and 

 vegetable life, that they form part of every thing 

 we taste or touch, but that for their perfect de- 

 velopement a suitable nidus is necessary, which 

 nidus is presented in an infusion of some kind or 

 other. These animalcular ova it would appear, 

 depend much for the form they are to assume wben 

 evolved upon the peculiar nidus in which they 

 are deposited ; for the same infusion, in different 

 stages of fermentation and putrescence, developes 

 different species of animalcules. Or perhaps the ova 

 themselves have distinct characters, and the infusion 

 may become successively adapted for the develope- 

 ment of the various species. Leaving this point 

 as one of mere conjecture, we pass on to observe, 

 that optical science has rendered these animalcules 

 legitimate subjects of natural history; and we are 

 consequently to acquaint ourselves, as before ob- 

 served, not merely with their extreme littleness, 

 but with all the peculiarities that constitute their 

 generic and special differences. We are indebted 

 to Dr Khrenberg, of the university of Berlin, for 

 much of the information we now possess, relative to 

 infusoria. Prior to his elaborate examinations, they 

 had indeed, to a certain extent, been classified by 

 Muller and others, but they were almost uniformly 

 described as atoms of gelatine matter, having no 

 internal organs, and nourished wholly by absorption. 

 In our necessarily brief description of this interest- 

 ing class of animalcules, we shall avail ourselves of 

 the kind permission granted us by Mr Pritchard, 

 to extract from his very recent and valuable publi- 

 cations in this department of zoology. " The term 

 animalcule, which implies nothing more than the 

 diminutive of animal, lias been commonly used to 

 denote those living creatures inhabiting fluids, 

 which are too minute to be scanned, or even seen, 

 by the naked eye : such, for instance, as those 

 produced in inconceiveable numbers from infusions 

 of animal and vegetable matter : it comprehends as 

 well such as are found in, and are peculiar to, the 

 bodies of larger animals : this latter class, however, 

 does not fall within the province of this work." 



" In the variety of systems that have been put 

 forth, respecting these extraordinary creatures, the 

 main characteristics of each have referred either to 

 a difference in their size, or to the general appear- 

 ance of their external forms: the present design, 

 however, is not to investigate the value of these. 

 Until the introduction of vegetable colouring mat- 

 ter into the fluid, which supplies them with food, 

 an experiment that has been attended with very 

 successsful results, these creatures were com- 

 monly supposed to be entirely devoid of internal 

 organization, and to be nourished by the simple 

 process of cuticular absorption. By the applica- 

 tion of coloured substances, which, moreover, have 

 been found to invigorate, rather than depress the 

 animalcule, and to maintain it in the full exercise 

 of all its functions, this erroneous notion is set at 

 rest, and an internal structure is discerned in some, 

 equal to, if not surpassing that of many of the 

 larger invertebrated animals, and comprising a 

 muscular, nervous, and, in all probability, vascular 

 system ; all wonderfully contrived for the perform- 

 ance of their respective offices." 



The most obvious portion of their internal 

 structure is undoubtedly that connected with the 

 digestive functions ; and hence it is that Ehrenberg 

 has selected this as the leading feature of his ar- 

 rangement, denominating his two grand divisions of 

 the Phytozoa, Polygastrica and Rotatoria; the 



former of which includes sucli as are possessed of 

 several distinct stomachs or digestive sacs ; and the 

 latter such as have true alimentary canals, and ro- 

 tatory organs, provided with a number of cilia 

 aptly disposed for promoting the objects of life : 

 these two grand divisions of the Phytozoa, are after- 

 wards subdivided into families, and other minor 

 branches. The cilia, in their different combina- 

 tions, supply the means of locomotion, propelling 

 the creature, in many cases, with great rapidity 

 through the water: they are apparently stiff like 

 eye-lashes ; and from Dr Ehrenberg's description of 

 some of the larger ones, they issue from bulbous 

 substances at their bases, and being acted upon by 

 muscular fibres, are capable of being moved to and 

 fro, in particular directions, so as to occasion a cur- 

 rent of the fluid to flow towards the mouth of the 

 animalcule, by which it is furnished with fresh 

 water, or food. They are sometimes disposed, as 

 before stated, round certain organs of a circular 

 form, which, on account of their peculiar vibrations 

 giving the appearance of a rotatory action, are 

 termed rotatory organs. A second curious feature 

 in the construction of some of these minute crea- 

 tures, are the sete, or bristles, attached to the surface 

 of their bodies': these short movable hairs in all 

 probability act as fins, and contribute greatly to 

 their means of motion. The third feature are the 

 Uncini, or hooks, setaceous appendages curved at 

 their extremities, and serving the creature to at- 

 tach itself to any object it chooses. A fourth are 

 the Styli, jointed at their bases, and differing from 

 the cilia in respect of their being unable to effect a 

 rotatory motion : these, however, are more flexible, 

 and have more play than the setce. Independently 

 of these peculiarities, some animalcules possess the 

 extraordinary faculty of thrusting out, or elongat- 

 ing, portions of their bodies at various points, 

 which assuming the appearance either of legs or 

 fins, are termed variable processes, and enable the 

 creature to walk or swim." 



" It was a favourite hypothesis with naturalists, 

 some years ago, that the class of animalcules under 

 consideration, was entirely nourished by cutaneous 

 absorption, and that no suitable organs for trans- 

 mitting and digesting food were discoverable. 

 Baron Gleichen was the first who brought the 

 truth of this theory to the test ; for having tinged 

 some water containing animalcules with carmine, 

 he found on the second day, that only some dis- 

 tinct cavities in the interior of their bodies were 

 filled with the colouring matter, evidently demon- 

 strating the existence of an alimentary structure : 

 here, however, he left the subject, and it is to Dr 

 Ehrenberg's further investigation of it, that we are 

 indebted for an accurate description of their differ- 

 ent forms. In more recent experiments it has been 

 found advisable to employ vegetable colouring sub- 

 stances in their pure state ; such, for instance as 

 sap-green, and indigo, which, together with the 

 valuable accession of an excellent instrument, en- 

 abled the doctor to contribute much to our pre- 

 viously imperfect knowledge of this branch of 

 natural history." 



" In the selection of vegetable substances for 

 infusions,'' (for procuring animalcules) " such as 

 stalks, leaves, flowers, seeds of plants, &.C., care 

 must be taken that there be no admixture of qui- 

 nine (bark) in them, or the intention will be frus- 

 trated. Immerse these, whatever they may be, 

 for a few days, in some clear water, when, if the 

 vessels which contain them be not agitated, a thin 



