NATURE 



[October 24, 19 12 



to. Moreover, he is mistaken in supposing that I am 

 not acquainted with the facts and theories as to the 

 structure and history of flint in its various conditions. 

 .As a matter of fact, this subject has occupied my 

 attention during the greater part of a lifetime. 



The specimens of "worked" flints from the sub- 

 Ciag detritus-bed— dealt with in my recent paper in 

 the Phil. Trans. — have now been presented to the 

 Department of Ethnology of the British Museum 

 iBloomsburv). and it is now possible, for those 

 who wish to do so. to study the actual material upon 

 which mv statements are based, and to discuss them 

 with the needful preliminary knowledge of the things 

 under discussion. E. Ray Lankester. 



20 Thurloe Place, South Kensington. 



Nautilus Pearls. 



The letter from Mr. H. Lyster Jameson in the last 

 number of Nature reminds me that I have in my 

 possession a small pearl that is alleged to have been 

 found in a Nautilus. It was given to me by a Dutch 

 magistrate in North Celebes, who had in turn received 

 it from a native. It is irregularly pear-shaped, and 

 weighs 27'5 grains. 



As there is so little substantial evidence that this 

 or any other pearl or stone has really been formed 

 within the body of a pearly Nautilus, I have never 

 felt disposed to assert that I possess a Nautilus pearl. 

 However, there can be no doubt whatever that there 

 is a widespread belief among the natives of the Malay 

 Archipelago and Polynesia that such pearls are occa- 

 sionally found, and although in the Sulu Archipelago, 

 according to Mr. Haynes's account, they are regarded 

 as unlucky, in Celebes they are treasured as charm 

 stones that bring good fortune. 



Rumphius, in his " D'Amboinsche Rariteitskamer," 

 published in 1702, gives a description of such a stone 

 found in a Nautilus, and relates an interesting story 

 connected' with it. He says that the stone belonged 

 tn a Chinese woman in Boero, who had kept it in a 

 little box and treasured it as a charm. One day she 

 discovered that it had given birth to another small 

 pearl, and later on two other small pearls were born 

 in a similar manner. This statement reminded him 

 of the story told bv Pliny in Lib. 37 of the reproductive 

 stones called Peantidcs and Gemonides. 



Sydney J. Hickson. 



TIio Universitv, Manchester, October iS. 



Sailing Flight of Birds. 



There can scarcely be a doubt that Prof. E. H. 

 Hall has given, in Nature of October 10, the true 

 explanation of the sailing flight of gulls when they 

 follow a ship without any movement of their wings. 

 When there is a fairly strong head-wind or a wind 

 which, without being strictly a head-wind, makes a 

 small angle with the line of the ship's course, the gull 

 has an up-current of air provided for him which will 

 not only support him, but which, if he inclines his 

 bodv (and supporting surfaces generally) slightly 

 downward, will enable him to make headway. 



Sometimes tlie gull will hang directly over the 

 stern, at others slightly to windward, at others, but 

 I think not so often, slightly to leeward. Some ex- 

 periments which I once made with a vane that worked 

 vertically showed that when the wind strikes a bank 

 six feet high at right angles, there is a steady up- 

 current four yards to windward. Five yards to leeward 

 there was a down draught, and some ten yards to lee- 

 ward irregular up-and-down draughts. Recently in 

 Texel I frequently saw gulls hovering with motionless 



NO. 2243, VOL. go] 



wings a few yards to windward of embankments some 

 twenty feet high. F. W. Headley. 



Haileybury (Hertford), October 13. 



The Zodiacal Light. 



As of possible interest to some of your readers \ 

 beg to report to you a phenomenon which I have 

 observed here during the last ten days. It may be 

 described as follows : every evening after sunset 

 when twilight has completely died out of the western 

 sky there is observable an illumination, starting due 

 west and extending upwards to a height of about 40° 

 above the horizon, fading away towards the top; in 

 character it is much like the Milky Way, a little 

 broader at its base, slightly less brilliant but more 

 uniform. It extended this evening (August 10) from 

 a point due west at 7.30 p.m., Gallegos mean solar 

 time, upwards to a height of about 35° from the 

 horizon, 'in the direction of the planet Jupiter, inclin- 

 ing towards the north at an angle with the horizon 

 of about 60°. A curious fact I noticed in connection 

 with this phenomenon was that it was best observed 

 when the rays from it were allowed to fall on the 

 periphery of the retina, as when the eyes were fixed 

 O'l a point about 20° distant. It could be observed 

 for about two and a half hours after sunset, gradually 

 setting in the west. I presume this is the zodiacal 

 light, but as I never noticed the same phenomenon in 

 these latitudes (51° south) before, I thought it wortli 

 while mentioning the fact. E. G. Fenton. 



Rio Gallegos, Patagonia, Argentine Republic, 

 August 10. 



Colours of Plasmodia of Some Mycetozoa. 



To my communication under this heading that 

 appeared in Nature of June 23, igio, p. 489, allow me 

 to make the following additions : — 



Species of Mycetozoa. 



Physarurn variahile, Rex, 

 var. sessile, Lister 



Colloderma oculatum, G. 

 Lister 



Coloi 



Orange 



of Plasmodi: 



jllow. 



Cribraria iiitricata, 

 Schrad. 



Perichacim chrysospcrma, 

 Lister. 



Dingy watery-white witiT 

 greenish or olivaceous 

 tinge, then ochraceous, 

 ultimately ferruginous 

 and dirty throughout. 



Pitch-black when the 

 Plasmodium is thick, 

 and oil-brown when it is 

 thjn ; in either shade it 

 closely simulates the 

 solution of asphalt in 

 oil of turpentine. 



.Stated to be pale brown 

 in Lister's " Mono- 

 graph," second edition, 

 191 1, p. 248, but I 

 found it to be pallid 

 pink. 



Said to be yolk-coloured 

 in the same work, 

 p. 95, but I found it 

 milky, then cream- 

 coloured. 



Since mv letter above mentioned was published, I 

 have gathered nineteen species new to Japan, which 

 make the native Mycetozoa taken altogether amount 

 to 105 species, of which three are new to scaence, viz. 

 Arcyria glaiica. Lister, Hemitrichia minor, G. Lister, 

 and Diachaea rohusta, G. Lister. 



Kumagusu Minakata. 



Tanabe, Kii, Japan, September 17. 



Crateriwn 

 Rex. 



concinntim. 



