ii 4 



NA TURE 



[July 



1922 



and where the light approaches in two regular streams 

 of equal concentration. The difference is due to the 

 position of the opening BC relative to collision centres 

 below it within less than free path distances, from 

 which the approaching molecules will start, with 

 equal probability of movement in all directions. The 

 molecular problem would thus appear to approximate 

 to the simple statement in my paper, in which the 

 " points O" may consequently be regarded as little 

 elements of area, and to be quite different from light 

 calculations such as the one worked out above. 



In connexion with Mr. Atkinson's claim that ele- 

 mentary principles would be defied if an effect were 

 to occur, it is not obvious why this should be so 

 (provided, as has always been emphasised, that the 

 apparatus shall be sufficiently small to deal with the 

 oscillations or movements of molecules individually), 

 any more than in the case of the energy of a swinging 

 pendulum being converted into useful external work 

 by the agency of suitable mechanism. 



The argument that if light is reflected, then 

 molecules must actually be so similarly, to which 

 Mr. Atkinson strongly objects, does not appear 

 in my paper, where, in fact, the exact opposite is 

 stated (page 1053, line 26), although such reflection, 

 as an average effect, is not regarded as being im- 

 possible. Arthur Fairbourne. 



King's College, University of London, 

 Strand, W.C.2, June 22. 



Polarisation of Diffused Light under the Sea. 



I took advantage of a recent opportunity to make 

 some observations on polarisation of the diffused 

 light in sea-water, using a detector consisting of 

 four quartz prisms made up on the De Senarmont 

 principle, combined with a Nicol. The depth was 

 30 feet, the sea-water very clear, and the day cloudy, 

 with no trace of sky polarisation. The diffused light 

 at the bottom was quite strongly polarised, the water 

 behaving like a turbid medium observed at right 

 angles to the incident beam, the plane of polarisation 

 being perpendicular to the surface. 



The greatest intensity was in the horizontal 

 direction, diminishing rapidly as the angle of elevation 

 increased, and disappearing completely long before 

 the direction became nearly vertical. Repeated 

 observations created a strong impression that the 

 direction of maximum polarisation was not exactly 

 horizontal, but very slightly inclined downwards. 

 However, the difference, if any, was so small that it 

 must be regarded as doubtful. 



I should have liked to repeat observations on a 

 day of blue sky, but the opportunity did not arise. 

 The light from the sandy bottom and from a white 

 plate did not show any trace of polarisation. 



Apart from polarisation, it was interesting to 

 observe the surface. It is not easy to look vertically 

 upwards in a diver's helmet, but there was evidently 

 a circular luminous area directly overhead, rapidly 

 falling off in intensity without any sharpness of tran- 

 sition. It was a kind of inverse penumbra effect. 



E. E. Brooks. 



Leicester City Technical School, June 30, 1922. 



Discoveries in Tropical Medicine. 



In Nature of June 24 Sir Kay Lankester repeats 

 his statement that the transmission of Filaria 

 bancrofti from infected to healthy men through the 

 intermediation of the mosquito is not a sufficiently 

 established fact. I trust you will permit me to state, 

 for the benefit of those of your readers who may be 

 puzzled by an assertion so discordant with current 

 teaching, that at this school we shall always be happy 

 to demonstrate sections of mosquitoes and of human 



NO. 2751, VOL. I io] 



lymphatic gland that show the facts of that trans- 

 mission. 



With regard to Sir Ray Lankester's other em- 

 phasised statement that " Manson did not discover 

 the part played by the mosquito " in this transmission, 

 we shall be happy to show Manson 's original charts 

 and drawings made in Amoy, and other necessary 

 evidence that Manson did follow out the development 

 of the embryonic and larval Filaria bancrofti in the 

 stomach and body-cavity of the mosquito. This 

 evidence, quite apart from any additions to it or 

 corrected inferences from it, establishes the essential 

 fact that the insect is the vital agent of transmission, 

 since it releases the imprisoned embryo from the 

 blood-vessels of its host, nourishes it until certain 

 necessary organs are developed, and thus enables 

 it to make a start in life. A. Alcock. 



London School of Tropical Medii ine. 



Endsleigh Gardens, Euston Road, N.W.I, 



July 5- 



Ouramceba. 



With regard to the notes by Messrs. Rowley and 

 Kirkpatrick in Nature of July 8, on the occurrence 

 of Leidy's genus Ouramceba in England, it may be of 

 interest to record that I have recently (a few days 

 before their letters were published) found one speci- 

 men of Amoeba proteus in this condition, i.e. infected 

 with a parasitic alga. I was very much interested, 

 because I have never encountered anything like 

 Ouramoeba in the neighbourhood of Manchester, 

 where I have chiefly collected. 



I have not Leidy's book with me now for reference, 

 but am familiar with his figures, and have no doubt 

 whatever that the specimen which I found corre- 

 sponds exactly with his genus Ouramceba. It was a 

 typical A mceba proteus, with filaments of the parasitic 

 alga projecting fanwise in two tufts, one tuft on each 

 side, nearer the end which was posterior in progression. 

 Its vitality certainly was not impaired in any way. 



This specimen was taken from a small tarn near 

 Crag House farm, not far from Windermere. The tarn 

 lies at the summit of a ridge, the altitude of which is 

 given as 700 feet on the Ordnance Survey map. It 

 should be emphasised that, although the tarn contains 

 ordinary Amoeba proteus in fair abundance, only 

 one specimen has so far been seen which was infected 

 with the alga. The other fauna of the tarn include 

 very numerous Thecamcebida, some Flagellata, 

 Ciliata, desmids, diatoms, etc., a fauna which 

 corresponds fairly closely with that dealt with by 

 Leidy in his book, and which is probably typical 

 of open moorland country at high altitudes. 



Amoeba proteus is found in other tarns in this 

 neighbourhood ; but I have never seen any other 

 specimen infected with the alga from these other 

 localities, although, since reading Mr. Rowley's letter, 

 I have again searched fresh material. 



G. Lapage. 



Bowness-on- Windermere, July 10. 



Histological Stains. 



With reference to Dr. Nierenstein's remark (July 8, 

 p. 33) that the British dye industry would do well 

 to pay attention to the supply of dyes suitable for 

 histological work, it should be recorded that in khm, 

 when pathologists here had a difficulty in getting 

 satisfactory stains, the Pathological Society of Great 

 Britain and Ireland approached Dr. Levinstein in the 

 matter and received from his organisation ample and 

 most useful help which carried us on until reasonably 

 good stains became available again through the 

 ordinary trade channels. A. E. Boycott. 



July 8. 



