HARDWICKE'S SCIENCE-GOSSIP. 



59 



order to get a fair idea of the class. Although I only 

 commenced the special study of the Rhizopoda about 

 three months ago, I have already collected over one- 

 third of the known fresh-water species, so far at least 

 as these are recorded in Professor Leidy's great work ; 

 and in addition three or four species apparently 

 unknown to that authority ; all in four or five 

 l^laces, within a mile of my own house. In future 

 papers I propose to describe these forms, and to give 

 drawings of the principal varieties, in order to 

 revive an interest in a somewhat neglected class of 

 animals. 



The Rhizopoda are microscopic beings, the 

 majority of which are invisible to the naked eye ; 

 they are essentially aquatic, being found in ponds, 

 <litches, lakes, marshes, bogs, and in the sea. They 

 appear to have been the first representatives of 

 animal life on earth ; and if the theory of evolution 

 be correct, they represent our own remotest ancestors. 

 They constitute a class of micro-organisms of the 

 most simple character ; there is no distinction of 

 tissues or organs, but their animal substance is homo- 

 geneous, contractile and translucent, resembling a 

 tenaceous mucus or soft tremulous jelly. This jelly 

 •substance, in the living state, is constantly changing 

 its form by expanding at one or several points into 

 processes of ever-varying dimensions, arrangement, 

 and number. These are used as organs of locomotion 

 and prehension, and frequently branch. From the 

 appearance of these temporary organs resembling 

 roots, this class of animal has received its name of 

 J\.hizopoda, literally, root-footed. Generally speak- 

 ing, especially in the naked forms, this colourless 

 jelly includes coloured food-particles, principally 

 microscopic algae in various stages of digestion, and 

 tnumercus globules, granules, and various foreign 

 particles, such as sand-grains, all of which tend to 

 diminish the transparency of the animal, and often 

 impart considerable colour. The internal portion of 

 the animal appears somewhat more fluid than the 

 •exterior, although in no case is there a true mem- 

 branous covering. The terms endosarc and ectosarc 

 are used to express this difference, which is more 

 marked in the Order Lobosa than in any other. 

 JNIany of the animals are capable of enclosing them- 

 selves in a shell or test of various figure, consistence, 

 and complexity, and such variations serve to separate 

 the Rhizopods into families and genera. The 

 testaceous forms include the charming Foraminifera 

 and Polycystina, the exquisitely beautiful shells of 

 which are formed in the one case of carbonate of 

 lime, and in the other of silica of most glassy 

 transparency ; but as these are (with one exception) 

 exclusively marine in their habitats, we omit all 

 further reference to them in these papers. The 

 fresh- water Rhizopods form their tests or shells of a 

 variety of materials ; some of a horn-like substance 

 ■ called Chitine, similar to that which gives strength 

 to the integument of insects ; others form neat, box- 



like cases, made up of minute sand-grains or of 

 diatoms, separately or mixed ; while another section, 

 having made a further advance in architecture, 

 build up their tests of rounded, oval, or rectangular 

 plates, of chitinous or silicious material, which, over- 

 lapping in various ways, form definite patterns. Our 

 district is fairly rich in these charming forms ; 

 although the greater number of them are inhabitants 

 of sphagnous swamps. In most of the genera there 

 is a more or less granular spot called the nucleus, 

 which is considered as the centre of vital activity. 

 Many authorities attach great importance to the 

 presence or absence of this organ, but it is, I believe, 

 a fact, that in the lowly organisms we are now 

 considering, it cannot always be demonstrated, and 

 in some cases is undoubtedly absent. There is, 

 however, another organ which is rarely absent — 

 sometimes indeed there are considerably more than one 

 (in Arcella, for instance) viz., a contracting vesicle ; 

 this presents itself as a "clear, colourless, or pale 

 roseate sphere, which is observed very slowly to 

 enlarge, then rapidly to collapse, and for a moment 

 to disappear, again to reappear, commonly in the 

 same position." This occurs with a certain degree 

 of regularity. The phenomenon is remarkable, and 

 probably serves a respiratory, and possibly an 

 excretory function. 



A few words on classification, which is simple, and 

 easily mastered, will suitably conclude this introduc- 

 tory paper. The class is divided into five orders : 

 Protoplasta ; Heliozoa ; Radiolaria ; Foraminifera ; 

 and Monera. The first order is divided into two sub- 

 orders, Lobosa and Filosa j the former with thick, 

 finger-like, or lobose processes or pseudopods ; the 

 latter with filamentous or thread-like pseudopods. 

 The fresh-water Rhizopods are, with one or two 

 exceptions, contained in the first two orders. Proto- 

 plasta lobosa has eleven genera and about forty-three 

 species, and contains such well-known forms as 

 Amoiba, Difflugia and Arcella ; P. filosa has six 

 genera, and about seventeen species, many of them 

 most charming animals, having most beautifully built- 

 up tests ; Heliozoa contains eleven genera and about 

 fifteen species. While the order Foraminifera has but 

 two fresh-water species, Gromia turricola and Biomyxa 

 vagans. Monera, constituted by Haeckel to contain 

 those Rhizopods destitute of nuclei, may be discarded, 

 as many of the forms for which it was created 

 (Foraminifera, &c.) have been proved to be nucle- 

 ated. This gives us thirty genera, and about seventy- 

 seven species. I have little doubt, however, from 

 my own limited experience, that this number might 

 be materially increased if Microscopists would only 

 pay some attention to this interesting but neglected 

 class of animals. In ray next contribution, I propose 

 to describe the Rossendale forms of the naked, lobose 

 Protoplasts. 



J. E. Lord. 



Rowtenstall . 



