WAYS OF THE WILD.

Auckland Star, Volume LXVIII, Issue 156, 3 July 1937, Page 1 (Supplement)

WAYS OF THE WILD.

THE FORAMINIFERA. EEMAEIABLE MICROSCOPIC CBEATVBES. (By A. W. B. POWELL.) One of the strange thing? about Nature is that its smallest members are often builders of the greatest "works. The minute coral polyp is the bmsis of the vast Barrier Beef, of Queensland, most of the island of Barbados is built up of the skeletons of microscopic animals, radiolarians, that once accumulated in the ocean deptfc, and it is estimated that 48,000,000 square miles of the ocean floor is made up of a thick deposit of the shells of globigerina. tiny foraminifera. Even the great pyramids of Egypt are built of limestone that was formed millions of years ago at the bottom of the sea through the gradual accumulation of the dead shells of millions of foraminifera. Strangely enough these foraminifera are near to the lowest known forms of animal life, for they belong to the protozoa. to which belongs also the amoeba. Unlike the amoeba, the foraminifera form shells, often of the mast exquisite beauty and perforated with minute holes, or "foramina"—hence their name. More than 2000 living and fossil species are now known to science, and all save one small group are marine. Some are to be found between tidemarii#. others on the sand or mud, or adhering to seaweeds, while some are what is called palagic—that is to say they drift about near the surface in the ' open ocean. How the Sheila Are Built. 1 Though the-living jelly-like substance which fills these shells is, so far as we can analyse it, of exactly the same nature as that of amoeba, yet in the presence of that shell we have proof enough of the existence of some inherent and mysterious difference in the qualities of thw supposedly common substance. For it can not only extract carbonate of lime from the sea-water, but fashion it into a casket such as no human craftsman could hope to imitate. ! Through the perforations in the shells of the foraminifera the soft jelly of the < bodv or "protoplasm" protrudes, to invest the shell and form a delicate network of threads for the capture of its food. ! The shells of the foraminifera are built ' up in a very interesting way, for they begin as a simple sphere, with a hole at the top. As growth proceeds, the jelly-like substance exuding from the mouth of the shell forms a second and larger chamber. And this process of growth may go on until, in some species, many such chambers are formed, the mouth of each opening into the floor of the one above it. In some these chambers are ranged in a straight line; in others they give rise to a coiled shell like that of a nautilus, thereby completely misleading the earlier naturalists, who supposed them to be microsopic relatives of the great nautilus, which is a shellfish. There are yet other specics which build a shell of sand-grains, the flinty, glassy - t looking spicules of sponges or the beau--j tiful anchor-like glassy plates in the seacucumbers, cementing these varied materials together by means of some adhesive formed by the jelly-like substance of their bodies. Some use the empty shells of other foraminifera. Those which use only grains display what some have averred to be a deliberate choice in the kind of sand that is used. One species will take up only minute fragments of magnetite, garnet, or topaz; another quartx-grains. We seem to have here evidence of conscious selection, many possible kinds of material being rejected for that of its ; choice. i Nature and Life Habits. A far more satisfactory explanation lies in the specific gravity of the material used, and a subtle responsiveness to touch. As a magnet may be said to "select"' only particlos of steel or iron filings, so in like manner these tiny creatures "selecf only such building materials or such food as its living jellylike tissue has become adjusted to adopt. Most foraminifera are bottom living forms, crawling slowly about on the surface of the ocean-bottom muds and roees or attached to various objects on the bottom. Pome are attached to hydroid stems and seaweeds. In fact, quite a number may be collected locally by simply washing seaweeds in fresh water and examining the residbe under the microscope. The rate of movement in the foraminifera is very slow, yet when com-, pared with their size, they may be considered capable of covering considerable distances. In order to pick up material for the formation of their shells certain kinds which show this selective ability must cover considerable distances. The most rapid movement so far observed in the foraminifera ii at the rate of one millimetre per minute. The food of the foraminifera. so far as is known, consists of vegetable material in the form 0 micra-K.v>pic diatoms and minute seaweeds. 1 _ j Factor in Natural Oil Storage. v T' l ® largest known foraminifera. is Aumniuhtes. the one referred to earlier as forming the limestone from which the pyramids were built. Tlkw fos-i] species once attained the size of a fiveshilling piece, and there are areas of the Egyptian de-ert to-day w here lhe fossil -hells of t luv-e f :»ra-.ii : .uifera —till ]av ; I'kw. so thick thor it is difficult U, | walk over them without slipping on their smooth surface'*. The-e deposits were con-j.lercd l.v 1 lie ancients to ]>e t lie jH'trificd remain- of bean* left behind l>y the builders'of the pyramids. Tli i- nnmmulitlc limestone, as it is called, extend- in a continuous mass froni .Africa into Kurope on the north and sweeping eastward* through the Alp-. Carpathian- oml Caucasus across A.-ia to ( hina and Japan: proof of the former extent of a vr.-l ocean now drv land. 1 oramimfcra have recently come into prominence owing to their u<-e in determining sub-surface structures bearing ujH.n the location of ( ,j] field*. Many of our -edimentary ro;-ks contain no vestige of larger fossil organisms, but almost invariably they will be found to contain well-preserved remains of these minute foraminifera. The almost complete range or sequence of fossil fora- ! minifera thus available enables the palaeontologist to determine minutelv the characteristics of each stratum encountered during boring operations, and by systematic br»ring it is possible to recognise individual layers and thus obtain a picture of the conformation of strata hundred.? of feet below the s„ r . face. In this way anti-rlinal folds, that is. cv/ved strata inclined downwards at the rides, are l<»cated. and these, if the super:ni]»osed stratum !s impervV.us. allows of the imprisonment jtnd accumulation of the valuable 1 natural reservoirs of petroleum.