jANl'ARY, 19i; 



KNOWLEDGE. 



a 



parallel to the base of the cone, we get a cone and a frustum 

 formed, the cone being longer than the fnistiun and apparently 

 much larger. On determining the voliiiiics of these two 

 portions, however, the surprising fact is revealed that the 

 cone has not more than two-thirds the cubic contents of the 

 frustum. However, the blunt (frustuin) portion includes half 

 of the large nucleus of the plant and of the large vacuoles 

 around the nucleus, which do not appear in the cone end. 

 Thisblunt end is the one which has to undergo reconstruction, 

 a process requiring the using up of a good deal of material like 

 starch, of which this portion contains more than the cone. 

 Hence this new half cannot be said to "grow out" in the 

 sense of having to grow in order to become as large as the 

 pointed end, since it contains quite as much material as the 

 old end. There is a re-shaping of this material, but both ends 

 take part in the growth that is to produce again a normal size 

 in the individual. 



The division process in the two species of Clostcriiiiii 

 examined by Lutnian occurs at night time, and takes two 

 nights for its completion. The chromatophore divides the 

 first night ; while on the second night the nucleus divides, 

 between 10 p.m. and 5 a.m.. the new half becoming practically 

 symmetrical with the old one by 9 a.m. Clostcriuiii as seen 

 in the daytime has its chromatophore divided into halves, 

 resulting from the chromatophore division of the preceding 

 night, and the two halves are also to be regarded as a prepara- 

 tion for the division of the nucleus and cell the following 

 night — providing it has succeeded in storing enough food 

 material to make the process possible. 



Leaving aside some interesting points in reference to nuclear 

 division, especially the relations between the central mass 

 (micleolus) of the nucleus and the formation of the chromo- 

 somes. Lutnian's observations clear up various questions 

 regarding the structure and affinities of the Desmids. In 

 Closteriiini itself, for instance, the method of origin of the 

 two daughter chromatophores by constriction expl.ains the 

 fact that the ridges of the chromatophore on each side of the 

 nucleus correspond. The continuity of the outer granular 

 layer of protoplasm, in which the streaming occurs, is explained 

 by the fact that the constriction of the dividing chromatophore 

 is due to a ring-like vacuole formed within this granular layer, 

 which is, therefore, not divided but is left intact and enables 

 active streaming to take place between the two halves of the 

 cell. 



Again, the process of cell division supports the view that 

 the Desmids have arisen from filamentous Algae. The new 

 cross-wall grows inwards as a widening ring from the 

 peripheral cell-wall, in exactly the same way as in Spiro^yra. 

 and. it is only as the two new cells separate and the pressure 

 is relieved on one side of this wall that its shape changes. If 

 the cells did not separate, a filament being formed, each cell 

 of the filament would be essentially like a cell of Zypwina 

 with its nucleus at the middle, and a half of the symmetrical 

 chromatophore on either side. The pointed shape which the 

 new end assumes is clearly a secondary character, and we 

 may assume that Closteriiiin (and. therefore, the Desmids as a 

 whole) arose from filamentous forms, which developed the 

 habit of breaking up into single cells. 



The great majority of the Desmids are unicellular, but a 

 tendency to form filaments is seen in various genera, as 

 Cosmariitm. Riiastniiii, Staurastriini. The view that the 

 Desmids have arisen from filamentous forms, and are what 

 may be called a degenerate group, explains various points in 

 their structure and biology. e.|<., the highly-specialised external 

 characters of the cell and cell-wall, and the loss of sexual 

 differentiation of the conjugating cells. 



CHKMLSTRV. 



Bv C. .'XlNSWOKTH MrrcHKLi.. B..A. iOxon. 



K.I.C. 



INTERNATIONAL ATOMIC WEIGHTS FOR 1912.— 

 The Committee of International Atomic Weights has issued 

 its report and table of atomic weights to be used in the 

 coming year. The list now numbers eighty-two elements, 



having been increased by the addition of niton, the name 

 given to the emanation of radium. This substance is a 

 gas belonging to the argon group. Its atomic weight, deter- 

 mined by means of a micro-balance, was calculated to be 

 22J, but from other considerations the value 222-4 is regarded 

 as the more probable and is the one given in the table. 



Determinations made during the past year have resulted in 

 trifling alterations being made in the values of calcium, erbium, 

 iron, tantalum and vanadimn, while the experiments of Easley 

 (J. Aiiicr. Clwm. Soc. I'JIO, XXXII, 1117) have caused the 

 committee to change the atomic weight of mercuiy from 200-0 

 to 200- f). This is the most important alteration in the table. 

 .\s in the case of the last few years the whole of the values 

 are compared with oxygen as 16, and hydrogen as 1-008, and 

 the alternative values based upon hydrogen as unity are no 

 longer published. 



M.\RINE FIBRE. — Anew textile fibre has recently been 

 put upon the market under the name of " Marine Fibre," and 

 is sold at about ;^'5 per ton. It is derived from the bottom of 

 Spence Bay in South .Xustralia, and notwithstanding the fact 

 that it is soft and not very strong, it may be spun in admixture 

 with wool and other fibres. It differs from sea-weed in 

 structure and composition, and appears to have originated 

 from some land plant, such as New /Zealand flax. An account 

 of its chemical characteristics is given by Messrs. Green and 

 Frank {Joiirn. Soc. Dyem and Colourists, 1911, XXVII, 

 169), who point out that the high proportion of salt which it 

 contains renders it almost non-inflammable. It may be easily 

 dyed witli basic dyestuffs, in which respect it resembles jute, 

 but it has little aftinity for acid dyestuffs or sulphur dyes. 



STERILISATION OF WATER BY ULTRA-VIOLET 

 K.'VYS. — The use of the ultra-violet rays for the sterilisation of 

 water is now in general use, and various types of apparatus 

 have been patented. .-Xmong the most recent of these is the 

 apparatus of Henri Helbronner and von Recklinhausen of Paris 

 (Eng. Pat. 4<S9.T. of 1911). in which a mercury vapour lamp 

 enclosed in a quart/; chamber is innnersed in the water, while 

 a ball-float or similar device prevents the action of the lamp 

 taking place until the liciuid has arisen above the level of the 

 quartz chamber. 



.\ main essential for effective sterilisation is that the liquid 

 shall be relatively transparent to the radiation, since liquids 

 containingcolloidal bodies (gelatine, peptones, and so on), absorb 

 the rays, with the result that only the immediate surface 

 becomes sterilised. For this reason, as has been shown by 

 Rolle, (Vl'oc/i. Brail., 1911. .XXVIII, 533) the process cannot 

 be used for the sterilisation of malt liquors. 



In the case of clear water, however, the sterilisation is so 

 rapid that a simple apparatus has been devised by Rogier to 

 be attached to a water tap. This consists essentially of a 

 cylindrical mercury vapour lamp in a quartz chamber, which 

 is surrounded by an aluminium tube narrowing at one end, so 

 that the water comes close to the lamp on its way. It will 

 give a yield of two hundred to three hundred gallons of sterile 

 water per hour. 



The large plant installed at Marseilles for the sterilisation 

 of the drinking water works at a cost of 1-ld. per thousand 

 gallons, but this cost might be reduced by about half, and 

 would then be cheaper than sterilisation by ozone. .'\ccord- 

 ing to Courmout tChciit. /Celt.. 1911, XXXV. SOfil the sterilis- 

 ing process does not depiMul upon the formation of ozone or 

 hydrogen peroxide. 



CARBON MONOXIDE DETECTOR.— A simple and 

 effective apparatus, for detecting traces of carbon monoxide 

 in the air has been devised by Dr. Nowicki iOesterr. Zeit. 

 licrg.K. Hiitteinc. 1911, LI.X, 587), and should be found of 

 great use in mines. It consists of a glass vessel, the inlet and 

 outlet of which are provided with stopcocks. The air to be 

 tested is forced through the vessel by means of a rubber bulb, 

 until the air inside the flask has been displaced. The stop- 

 cocks are then closed, and a note taken of the time required 

 to blacken a strip of filter paper moistened with palladium 



