WONDERS OF THE MICROSCOPE

New Zealand Herald, Volume L, Issue 15234, 22 February 1913, Page 1 (Supplement)

WONDERS OF THE MICROSCOPE

No. 111. ■ \ ■ " ■'■■• '-.' PLANT OR ANIMAL? QUESTION OF BOUNDARIES. BY Q. A. .ItAWSOS. . . In former articles of this series I have stated more than once that the vegetable and the animal kingdoms are much more closely related than, most people have any conception of, and that it is impossible to define an exact , line *of ; demarcation between them. We shall now devote a little space to a closer, examination of this interesting problem. To state that in manycases there is almost no difference between pla;ats and animals may sound somewhat, startling to many of my readers, for to the average individual no distinction is, easier to make than that between the vegetable and the animal kingdoms; but then the average individual is usually concerned with the higher members of these two great divisions'of living tilings, where, of course, the difference is. seen at a glance. But science explores ' art invisible universe and takes cognisance of phenomena which are non-existent'to the unaided eye. ; ,"J , The intelligent worker with the microscope cannot prosecute ~ his studies of Protozoa and such simple organisms .very*• far before this question of boundaries obtrudes itself upon his notice and importunately demands an answer. There are numerous forms of life dwelling in nearly: every pond in regard to which much uncertainty exists as to their proper classification in the scale of organic life. The problem, What is an animal and what is a.plant? confronts Us at the outset. Under the searching analyses of microscopical and chemical investigation the former distinctions between plants and animals, depending upon modes of nutrition, reproduction, locomotion, th , presence of starch; and. so on, have one by one proved to be errone- .!- ous, ami to formulate a.V general principle} which will cover every case is almost impossible. As already,stated, when we are dealing _ 'with highly-developed '• forms, ■;-. the distinction can be decided upon at once,, but when we come to deal with lowly organisms, whose presence . can only be repealed to us by -the : aid of - the" highest' powers of the microscope, the case is very different. ■ As we descend the scale of life the two .1 great kingdoms converge more and more. : In fact, some scientists of high repute go ] so far as to say that there is really no distinction between the two kingdoms, but that the one merges by imperceptible degrees into ; the other. - . Viewed from an evolutionary standpoint —-and the standpoint which is not evolutionary,,,, is . not scientific—this close; affinity of the vegetable and animal kingdoms is quite natural and is what, the: theory of evolution would lead us to expect. Then, again, it is a very significant fact that between chlorophyll {the green colouring matter of plants) and haemoglobin (the red colouring: matter of the; blood) there is a fairly intimate chemical affinity. This points strongly to the conclusion that plants and animals are derived from i a common stock,,;= which millions of ages ago, in the world's early childhood, began to differentiate along separate and' ever-diverging I lines of development* , and organisation. - •' ' . .... . r , v The simplest known living organisms are : called monads. They can only be seen with very, high powers of -.the< microscope, and anyone watching a cluster of them for the i first time would probably - imagine that • there was difficulty in classifying them. But ; : to- 'tih.B man of science, who understands the nature of the problems involved, it' would baby no means an easy task. ' Suppose the zoospore-{that 13, a sport capable of moving about): of an undoubted plant ware placed side by side with a monad under the microscope, it would afford some indication of ; the difficulty of determining whether the monad was 'an animal or a plant. Even the subtlest;V analyses of the chemist- would leave us in uncertainty 'in : many instances, for we should discover some organisms, on the very border-line of the two kingdoms, in which no j'undoubted ; characteristics, of: either plant /or.- animal could be detected, 1 but thev would / exhibit /combinations of both. " -I ' s It was long supposed that; chlorophyll was an undoubted characteristic "of" the vegetable kingdom, but it is now known to occur /in ; certain animalcules.: / Cellulose, another substance universally iv found , iin? plants, and which : bi'ilds up/ their cell walls is now known ■'■■ to nomposo i the / outer layer of the ascidians or sea-squirts. /As: regards physiological processes, some vege- .' tables - actually assimilate and digest / starchy and nitrogenous matters which were once thought to belong entirely to animal nutrition. And some highlydeveloped plants Have moat elaborate aridingenious mechanism for the capture and assimilation of animal food,- in the- .shape of insects; such are the sundew and the Malayan pitcher-plants or nepenthes. Again, the phenomena of respiration affords no decisive answer to our question. As nearly everyone knows: plants, und«u\ the inflner.no of sunshine, drink in carbonic/ acid v gas and; give out nitrogen, and iib purify the atmesphere. All animals do the exact opposite: they assimilate oxygen and give out carbonic, acid. But in the dark the vegetable kingdom becomes animal, because then the plants give out- a- certain quantity of the carbonio acid gas which they . have drunk in during the : daytime. Thus there is, as one writer apt.'? states, a scientific "No Man's I.3 rid": wherein; dwell things innumerable, which, according to every canon that has yet been fried, cannot be finally arbitrated upon, and which may be called either animal or vegetable." . './■<:;■■■■ V.vV'NV.--/'''''' '■;•' Now that we have gained some notion of the difficulty and intricacy of the problem we have been dealing with, let us.,{■ ss'lsct, as an example, .a very pretty littl ). organism which is usually to be found in greatest abundance in dirty, sewerage-con- ! taminated water, although it is also common i'.r. ponds. It is a small infusor?;/«,'• known as Euj;ri«n.a—a simple unicellular or ganism, of .which there are several species comprising the genus. They are known as flagelh'te organisms, because from'wbiet may bt» called the head a long, slender, whip-like filament .;-. or flagelliun, projects, H r-hioh serves as a swimming organ. If one . <i?ainines a drop of water in which Engleme are numerous, ,the whole fi/'diof ! vskm will be seen to swarm ?■;;■>• -c feds • of tiny, elongated creatures, dart7 'fa ' a,c/y: :•'. in all directions.. Under a/,;{j | j,ly : ii,/h/i power they never fail to arrest alts .V/on, \. ani are well worthy of the closest ).. obser- I vation on ' account of their peculiar shape". / and habits. Normally they rathe i I6ng • and spindle-shaped, but oven as.we look at ; them their shapes, change. and assume various- i'ona;/'/ The '-tesro of these ':iii tie ,' creatures /is Euglena viriois. .' .ft is a liny! speck of bright green ; protopl.'issu. /--.'...1t/ = moves rapidly through the wirier, rollu; < over on its axis as it goes. Its. axm fe length/is about 1.-250 th of nr. ' inch,' , t ;v :#t ■■: it is quits invisible to the tokt-'i -'.ye. -.J' : .ivies' •S:s'Tna]s sometimes occu.'-.iv «r. jl ; raat niimbt-,,,; to make the v :.iiw Id ' which they live appear green, ar.i/ .'re-... quently they will cover the :stfA>ss i". I. stagnant pools in this manner. ';.-.- 1 /Vato '"'' which Englen® so abound is fcmid to gi ... off oxygen. This is what all. plants V<b ! under the influence of sunlight " from the J diatom to the cedar of Lebanon." • And s"v : ."s would appear that Eu^'ctra;is' ' a,plant:.:. '\V& have already seen that Awry : i microscopic slants— diatoms, for in- .1 stance— .apable of active, free move- i ment, while many undoubted amim';?, ,on .i the other "-'and, are fixed and statics tary, £ gj that mi; ! -lent is no criterion trudge t by But not so fast, however! Close to t the whip or. flagellum in Euglena 'is an; 1 opening, which closely resemble; a mouth., i There 1. : certainly an opening m the cell- 1 wall here, into which any: tiny particles of a flood floating, in the w,»tor find their : way, 1 and they appear to pass down a sort of a g'nb/ct' into what, for want, of <r; better i term, rv ' may tall a stomach. j; . This is- 1 distihcr'ly an Animal, and not a vegetable, l liethod of taking nourishment, ■'■"■■"'." , e