SCIENCE-GOSSIP. 



73 



CHAPTERS FOR YOUNG NATURALISTS. 



Some Lodgers in a Pond. 

 By A. F. Tait. 



'TJ'VERYONE is familiar with the appearance of 

 the brilliant green carpet that covers in many 

 cases the entire surface of ponds. This brilliant 

 green carpet is mostly formed of the common 

 duckweed, possessing roots of remarkable length — 

 about thirty times the size of the visible portion of 

 the weed, balancing the tiny plant, and anchoring it 

 securely to the surface of the water. Most of us 

 have read "Alice's Adventures in Wonderland," 

 and remember the strange creatures and remarkable 

 scenes Alice saw underground. If you can fancy 

 that we have removed a portion of this wondrous 

 carpet of emerald green, and descended under the 

 surface of the pond, you will see living creatures 

 more wonderful than ever were raised by the fabled 

 wand of the enchanter. 



Only a weed, you will say — let us pass on. We 

 will stop to look at it, for though only a weed, as you 

 say, it's one of the most wondrous things in the 

 whole vegetable kingdom. It looks like a festoon 

 of tiny leaves that might have been chosen by one 

 of the elves or fairies to fashion a garland with. So 

 much for its beauty, but the noteworthy fact about 

 it is that it is one of the very few plants in the 

 world that reveal to the observer the remarkable 

 feature of the swift circulation of the sap— the 

 plant's very life-blood, which rapid circulation is 

 called, in scientific language, cyclosis. Cutting off 

 a single leaf of anacharis, and placing it on the stage 

 of the microscope on a slip of glass — what do we 

 see ? Scores upon scores of brilliant green emeralds 

 flashing in the light, and chasing each other in 

 a swift and perpetual race round the cell-walls, now 

 running straight up where the course favours that 

 mode of motion, and now curving quickly round 

 like an arch, until the brilliance of the display, and 

 the perpetual movement of the cell-contents, weary 

 the eye, and you seek rest— and another object. 

 Before parting from this remarkable plant, we may 

 state one or two further noteworthy facts concern- 

 ing it. Anacharis is a native of America, and was 

 first seen in Britain fifty years since. Although a 

 very small plant, it increased with such rapidity 

 as actually to interfere with the navigation of 

 many of our canals and rivers, especially the 

 Cam and the Trent. The stem of the plant is 

 extremely brittle, and, when broken in pieces, 

 each little bit speedily takes root, and becomes 

 independent. Water-fowl, swans especially, are very 

 fond of it as food, and everyone who keeps an aqua- 

 rium will find anacharis invaluable for the aeration 

 of the water and the maintenance of its purity. 



Instead of entering the pond in our researches, 

 let us dip in a small bottle, and, having nearly 

 filled the little vessel, we hold it up to the light to 



examine our capture the better. What are those 

 remarkable-looking little green specks that are con- 

 stantly moving about ? Are they animal or vege- 

 table ? They are named Volvox globator, and the 

 question of their inclusion in the animal or vegetable 

 kingdoms has been hotly debated in the scientific 

 world. One eminent man has set it forth in bold 

 print that he will stake his reputation on it that 

 volvox is an animal. However, scientific people, 

 being only human, have been known to dogmatise 

 on insufficient data, and it is now proved that 

 volvox comes to us from the vegetable kingdom. 

 Let us take a little glass tube and, placing it into 

 our bottle of captures, examine for a minute the 

 wonderful object — barely the size of a pin's head — 

 which actually caused the scientific world to take 

 sides. We place a few of the tiny green globules 

 on a slip of glass on the stage of the microscope, 

 and what do we see ? During the two and a half 

 centuries that have elapsed since the first workable 

 microscope was made, the eye of man has not seen 

 a more beautiful or more wonderful member of the 

 minute world than that to which we now introduce 

 you. Desiring to supplement my information about 

 volvox, I looked up one of the authorities, but he 

 had not found out the secret of Huxley's and of 

 Tyndall's hold on their readers, that one may write 

 about scientific subjects in plain English, and may 

 make the subject as clear as an entry in the Direc- 

 tory, and yet full of interest. I refrain from in- 

 flicting the scientific bewilderment given by that 

 author upon you, and quote instead a description 

 of volvox which a distinguished Fellow of the Royal 

 Microscopical Society (Mr. John Badcock) has 

 given in " Vignettes from Invisible Life," one of the 

 most delightful books on microscopical science ever 

 written. "The Volvox globator is, as its name 

 implies, a rolling globe, each sphere having 

 within it a number of similar but only partially 

 developed smaller spheres, or globes, the whole 

 compound organism rolling and revolving in the 

 water forms a picture which once seen is never 

 forgotten. We call it a plant, for it is green and 

 has very few of the ways of animal life. Yet you 

 say it moves ? Yes, they are motile plants, and if 

 examined a little more closely are seen to be 

 covered with fine cilia, or thread-like hairs, which 

 by their constantly vibrating or lashing action are 

 believed to be the cause of the revolving motion 

 observable. It is a matter of common knowledge 

 that all vegetable life seeks the light ; now if a 

 number of these volvoces be placed in a glass jar 

 they will sink to the bottom when in darkness, but 

 in the light will all arise, and congregate together 

 at the side where there is most light, The cilia 



