132 



NATURE 



[October i6, 1919 



regulated to correspond with between 0-7 and 09 per 

 cent, of sodium chloride. 



It is strange that the mechanism governing this vital 

 regulation should not have been grasped before. The 

 cells and circulating medium are saturated with col- 

 loids, and this amount of o-y-o-g per cent, of saline is 

 just the amount the colloids are capable of holding 

 in cr.ystallo-colloidal adsorption. Any more is at once 

 filtered awav; any less, and life ceases. 



There are' manv other applications in biology and 

 medicine, but thev cannot be treated within the 

 compass of a letter. Benjamin Moore. 



14 Frognal, Hampstead. 



The Audibility of Thunder. 



It has been stated that thunder is not usually heard 

 at a greater distance than about twelve miles. This 

 may be so during the day, but at night it can fre- 

 quently be heard at a much greater distance from its 

 point of origin. Some years ago I timed an interval 

 between flash and sound over the sea, and found it 

 to be more than two minutes. During the storm of 

 September 5 last mv son, Lieut. F. O. Cave, and I 

 timed an interval by a method of counting seconds 

 often adopted bv photographers, with which method 

 we were both familiar; one of us made it 140 seconds, 

 the other 141 seconds. The flash was a particularly 

 bright one; we had previously heard fainter thunder 

 corresponding with less bright flashes, which were 

 presumably a good deal further away. 



On the night of October 1-2 a thunderstorm pas.sed 

 up-Channel to the south of this locality ; any rainfall 

 must have been beyond the Nab and the Warner 

 lightships, as both lights were plainly visible; their 

 distances are \']\ and i6|- miles respectively if fhf>- 

 are in their pre-war positions. With the help of an 

 electric clock, which moves on every half-minute, 

 supplemented by counting seconds, I made on.e time- 

 interval 120 seconds and another 170 seconds; then 

 with a stop-watch I timed an interval of 189 seconds. 



During the storm of October 1-2 the pheasants 

 crowed much more loudly than usual, especially at 

 the early rumbles of thunder, or else the audibility 

 was exceptionally good ; probably the latter was the 

 case, as the night was very clear and the air in the 

 valley from which the crowing came would have 

 been colder than the air here, a condition which would 

 probably be favourable for good audibility of sounds 

 coming from the valley, though it would scarcely 

 account for the audibility of the much more distant 

 thunder. It mav be worth noting that the false cirrus 

 above the thunder-cloud was lit up by light reflected 

 from the aurora which was extremelv brilliant at the 

 time. C. J. P. Cave. 



Ditcham Park, Petersfield, October 6. 



M 



OPEN-AIR NATURAL HI STORY A 



R. NOVELL'S book is the outcome of 

 years of patient study, and will be 

 welcome to botanists, entomologists, and bee- 

 keepers. It deals with the inter-relations of 

 flowers and insects, especially as regards pol- 

 lination; it "treats of plants alive and in the midst 

 of their home surroundings " ; it justifies the 



1 (t) "The Flower and the Bee : Plant Life and Pollination." By John 

 H. Lovell. Pp. xvii-t-286. (London : Constable and Co., Ltd., T919.) 

 Price los. dd. net 



(2) " Insect Artizans and Their Work," By Edward Step. (Hutchinson's 

 Nature Library.) Pp. x+3i8. (London : Hutchinson and Co., n.d.) Price 

 71. (tti, net. 



(3) " The Seashore : Its Inhabitants and How to Know Them." By F. 

 Robson. Pp. III. (London: Holden and Hardingham, Ltd., n.d.) 

 Price \s. 6ii. net. 



NO. 2607, VOL. 104] 



author's prefatory remark that "the identification 

 of a species should be regarded merely as an intro- 

 duction and the beginning of a friendship long 

 to be continued." The book is written with 

 enthusiasm and popularly, but it is a scientific 

 record of personal observations of great interest, 

 and it includes some notes on modern theories 

 which should be carefully considered. It is illus- 

 trated with conspicuously successful photographs, 

 which have been taken on panchromatic plates to 

 preserve in monochrome the proper colour values. 

 Beginning with a short historical sketch, in which 

 tribute is paid to Sprengel, Hermann Miiller, and 

 Darwin, the author discusses wind-pollinated 

 flowers, the r6le of hive-bees especially in relation 

 to blue flowers, the humble-bee's favourite flowers 

 which are mostly irregular in shape, the 

 short-cuts taken to the nectaries, the crab- 

 spiders which lurk in flowers and pounce on the 

 insect-visitors, the " oligotropic " bees that rarely 

 visit more than one kind of flower, the predomin- 

 antly reddish butterfly-flowers like pinks and some 

 Composite, the work of nocturnal moths in rela- 

 tion to flowers like evening primrose and honey- 

 suckle, the fly-flowers like Linna-ea borealis which 

 is visited by the dance-fly [Empis rufescens), and 

 those with nauseous odours like the carrion-flower 

 and the skunk-cabbage, the usually injurious visits 

 of beetles, flowers like wild roies, mulleins, and 

 poppies which are visited for pollen, not nectar. 



Mr. Lovell discusses the experimental evidence 

 of the value of having conspicuous flowers and of 

 colour-discrimination on the part of bees. In 

 regard to the latter, however, the discussion is 

 inadequate, for no experiments are conclusive that 

 do not distinguish between colour as such and 

 differences in intensity of illumination. A very 

 interesting general chapter deals with the colours 

 of flowers. Of the 4020 flowering plants in north- 

 eastern America, the greens, whites, and yellows 

 number 3001, while the reds, purples, and blues 

 amount to only 1019. The latter are, on the 

 whole, of more recent origin, and have evolved 

 from the others, the selective agency of insects 

 playing its part. In conclusion, the author dis- 

 cusses the value of bees in connection with fruit- 

 growing, and notably in securing cross-fertilisa- 

 tion, the importance of which is very strongly 

 emphasised. 



The author has written a fine book on a fine 

 subject, and his treatment should stimulate further 

 study. We wish that he had been able to devote 

 a special chapter to theoretical considerations, 

 for, though he believes in the transmission of 

 acquired characters, in the efficacy of insects as 

 selective agents, in orthogenesis carrying plants 

 beyond the limits of the advantageous, and in the 

 evolutionary importance of crossing, he says 

 tantalisingly little on these subjects. From an 

 observer of Mr. Lovell's experience we should like 

 to hear more. 



(2) Mr. Step has written a delightful book on 

 the industries of insects, which he arranges under 

 headings corresponding with human occupations. 

 He directs attention to the interesting fact that 



