April 21, 1882.] 



KNOWLEDGE 



527 





MACHINE OF SCIENCE 



MCAINUfyyORBED -£XACTUyDES CRIB££L 



LONDON: FRIDAY, APRIL 21, 1882. 

 Contents of No. 25. 



PAGB. 



A Btndy of Minots Life. No. III. 

 By Henry J. Slack, F.G.S., 

 F.R.M.S 627 



The Great Pvramid {lUtulraUd) . 

 BythoEiiitir 528 



Domestic Ventilation. By W. M. 

 Williams 630 



Found Linki (/Hu.<ra/cd). By Dr. 

 Andrew Wilson, F.K.S.E., F.L.S. 532 



Cambridge and Oxford Styles 533 



Rbtisws : — The Properties and Mo- 

 tions of Fluids (Iltuilrated) 634 



FAOB. 



Meat Preservation 535 



Solar Motion and Cometh from Out- 



side (lUwilraied) 6;)6 



Optical Blindness to Bed Light 536 



Bed Snow 536 



COBBEspoirDBNCE : — Caddis - Worm 



Cases— IntolliKenee in Animals.ic 638 



-Ynswers to Correspondents 539 



Notes on Art and Science 510 



Our Mathematical Column 510 



Our Chess Column 542 



Our Whist Column 544 



A STUDY OF MINUTE LIFE. 



By Henry J. Slack, F.G.S., F.R.M.S. 

 No. in. 



AN old e.xperiment that never fails to interest the 

 observer is the revival of dry, seemingly dead, 

 rotifers, by supplying them with water. The common 

 rotifer {rotifer vitlf/aris) is a curious little creature, showing, 

 as do nearly all its tribe, a very marked advance upon the 

 infusoria described in former papers. When full-grown 

 and stretched out, she — for it is the female that concerns 

 us — is about ^th of an inch long. The whole animal is 

 very flexible. It can elongate itself, wholly or partially, 

 by a process like sliding the tubes of a telescope, or can 

 swell out laterally like a pear or a ball. From the head it 

 can thrust forth cilia for swimming, and it can hold on by 

 its tail-foot, and crawl like a caterpillar. For respiration 

 and food-collecting, it puts out two groups of cilia, 

 which, when Lu motion, have the appearance of revolving 

 wheels, and hence it was called the "wheel animal- 

 cule." The so-called wheels produce strong currents in 

 the water, and their whirlpool character is easily shown by 

 putting in a little indigo or carmine. Rotifers are pro- 

 vided with elaborate organs, including a nervous system, 

 and in the large Pitcher Rotifers (Brachions) a moderate 

 magnification — say about fifty linear — is sufficient to show a 

 brain mass in the head very conspicuously. An observer 

 of the common rotifer, and of most others, is at once struck 

 with the sight of energetic work going on in the creature's 

 interior. The food particles are whirled down a gullet 

 into an internal mouth, commonly called a gizzard, and 

 this apparatus consists of several parts, two of which open 

 and shut with a motion something like that which may be 

 shown by putting two hands opposite each other, keeping 

 the wrists in contact, and making the bent fingers alter- 

 nately meet and separate. In the common rotifer, these 

 biting parts are what Gosse calls quadrantic, being like two 

 quarters of an apple, and furnished with crushing teeth to 

 act upon the food before it passes into the stomach. This 

 rotifer hatches its eggs internally, and the infant may be 

 noticed inside its mother, working its mouth, or gizzard, 

 before it leaves home and commences an independent life. 



These remarks may be a sufficient prelude to the ex- 

 periment of re\'iving these creatures from their torpid state. 



The first inquiry will be, how and where to find them. A 

 small wisp of hay, covered with water in a gally-pot, and 

 kept in a warm place, is pretty certain to exhibit some in 

 the course of a few days, but lower forms of Ijfe will appear 

 before then. The tine dust to bo found in glitters on a 

 dry day is very likely to contain some, and so is the dust 

 that can be shaken from tufts of moss on roofs or trees. 

 On a clear day in Feliruary, one such tuft, taken 

 ofi" the tiles, was shaken over a sheet of paper, and 

 a minute pinch of its dust placed on a glass slide, 

 in a drop of water, and covered with a piece of thin 

 glass. A convenient slide for these purposes is made 

 by cementing with shellac-glue on to an ordinary slide,* 

 three thin slips of glass, about three-si.'cteenths of an inch 

 wide, so as to form three sides of a small square. The 

 slide thus prepared should be laid flat, a drop of water put 

 in the middle of the square, and a covering-glass over it to 

 rest upon the thin slips. This makes a shallow water- 

 trough, and the cover is held sufficiently tight by the water 

 it comes into contact with. The grain or two of dust 

 obtained in the way mentioned exhibited no life of any 

 kind for a few hours, but in the course of the day a couple 

 of rotifers and one or two other things began to swim 

 about. The water in these small troughs, being little 

 exposed to the air, evaporates very slowly, and it is easy 

 to keep up the supply by putting a drop with a camel's-hair 

 pencil, so that it can run in. After looking for some time 

 at the revivalists, the slide was put aside, and examined a 

 few days afterwards. 



It was quite dry again ; the rotifers were discernible as 

 little lumps, and to all appearances dead. A drop of water 

 soon revived them, and this process may be repeated many 

 times. The creatures stand the amount of drying they get 

 under ordinary atmospheric conditions of evaporation, but 

 they may be over-dried by heat, and then no moistening 

 calls them to life again. The reports of various experi- 

 menters concerning the extent to which they may be dried 

 without being killed do not agree. Dr. Carpenter, Lord 

 Osborne, and others have found them uninjured by 

 drying that made them quite brittle ; while others, after 

 reducing them to that condition, have not succeeded in 

 restoring their animation. Probably the rate at which 

 the drying occurs has much to do with the result. Slow 

 drying is much less likely to cause any disruptive shrinkage, 

 and it gives the little animals time to protect themselves 

 from absolute dessication by a sort of mucus Mr. Davies 

 has described. 



When dried in the heat of a summer sun, and left as a 

 dust particle in a gutter or elsewhere, their life work 

 seems quite suspended, and in tliis they difler greatly from 

 the bats and dormice in their so-called hybernation. These 

 undergo no drying, though they lose fluid, and their vital 

 work goes on, though at a slow rate. In one of Marshall 

 Hall's experiments with a bat in the torpid state, its re- 

 spiration consumed nearly three-and-a-half cubic inches of 

 oxygen in sixty hours, and he remarked that in the 

 dormouse and hedgehog the sense of hunger seemed to 

 rouse them from hybernation, and that food conduced to a 

 return of the lethargy. It is also found that a dormouse 

 who is fat when the cold reduces him to torpidity, is lean 

 when the winter is past, and the season for renewed 

 activity arrives again. The mudfish passes into a state 

 nearer that of the rotifer, when the hot sun of Africa bakes 

 it in a mud-pie. The lethargy of hybernation' and also that 

 of heat and drought, enables animals to do without re- 

 spiration to an extent that would be quite impossible in their 



* Shellac dissolved in spirits of wine. 



Btronsr. 



Methylated will do if 



