July 29, 1922] 



NATURE 



■49 



tical importance. Mr. Henderson found that under 

 suitable conditions an a-particle may cause the de- 

 tonation of nitrogen iodide, about one a-particle in 

 10 7 or io 8 being effective. He suggests that other 

 unstable substances may be similarly affected. The 

 question naturally arises as to whether any of the 

 explosives commonly used are sufficiently unstable 

 to be detonated in this way. As they are all very 

 much more stable than nitrogen iodide we would 

 expect that the chance of an a-particle causing 

 detonation would be much smaller, so that an 

 explosion might only occur after a lengthy exposure to 

 a copious source of a-particles. Still, in view of the 

 almost universal presence of small traces of radio- 

 active matter, it is possible that some unexplained 

 explosions have been brought about in this way. 

 It would appear to be worth while to conduct an 

 investigation into the possible effect of a-particles 

 on various explosives and detonators. If it is found 

 that there is even the remotest possibilit}- of detona- 

 tion occurring, precautions should be taken in the 

 manufacture of explosives to reduce the radioactive 

 contamination to the lowest possible value. 



Horace H. Poole. 

 Royal Dublin Society, July II, 1922. 



Occurrence of a Crystalline Style in the American 

 Slipper Limpet (Crepidula fornicata) and its Allies. 



During recent investigations, carried out with the 

 aid of a Government grant, on the oyster beds in the 

 river Blackwater, freshly caught specimens of the 

 American slipper-limpet {Crepidula fornicata) were 

 examined fresh microscopically, and the interesting 

 fact was established that this species possesses a 

 crystalline style. Individuals which have been out 

 of water 24 hours or more still possess remains of 

 the style, which has undergone partial solution. 

 Crepidula differs therefore in this respect from the 

 native oyster (O. edulis), the styleof which is frequently 

 completely dissolved within 3 to 5 hours after indi- 

 viduals are taken out of water, and is completely dis- 

 solved in all specimens after about 10 hours out of 

 water. 



In the style of Crepidula occasional Spirochsetes 

 (Cristispira balbiani?) were seen, but not identified. 

 By analogy it was suggested that the allies of 

 Crepidula should also possess a crystalline style, and 

 an examination of fresh specimens at Plymouth at 

 once proved the surmise correct in the case of the 

 species Calyptnsa chinensis and Capulus hungaricus. 

 It is highly probable, therefore, that a crystalline 

 style is present in the whole of the Calyptraeids 

 and the Capulidae ; it is also not improbable that a 

 style may be present in all sedentary non-parasitic 

 Streptoneura. 



I have long suspected that a crystalline style — ■ 

 particularly in molluscs — is associated with a mode 

 of feeding which consists essentially in the capture 

 of planktonic organisms by mucus controlled by 

 harmonised ciliary mechanisms. The discovery of a 

 crystalline style in Crepidula and some of its allies, 

 which all feed in the manner mentioned, lends some 

 support to this idea ; but too little is known of the 

 habits of other gastropods which definitely possess a 

 style, to permit of a general correlation of the presence 

 of style with capture of food by means of mucus. 

 Some indications have been obtained by rough hurried 

 experiments that the style substance is a good solvent 

 for mucus ; and if this observation can be confirmed 

 it may well be shown th.it the dissolving of the 



NO. 2752, VOL. I io] 



mucus enveloping food-masses is one of the most 

 important functions of the crystalline style. 



J. H. Orton. 

 The Marine Biological Laboratory, 

 Plymouth, July 13. 



Sense of Smell in Birds. 



In the issue of Nature for June 17 there is a discus- 

 sion on the inadequacy of present observations on the 

 sense of smell in birds. Perhaps the following notes 

 would be of interest. They are from an account of 

 the habits of the birds of Trinidad which will be 

 published shortly by the Department of Agriculture 

 of that island. 



On September 20, 191 8, I observed large numbers 

 of the black vulture (Cathartes fastens) collected on 

 and round a field which had recently been experi- 

 mentally manured with liquid slaughter-house refuse 

 and could be smelt a quarter of a mile away, although 

 nothing was visible to the eye. A few red headed 

 vultures (Cathartes aura) were also present. In 

 Panama the same birds quickly found the body of 

 an animal that 1 put close to the' trunk of a thick tree, 

 quite invisible from above. 



Still more interesting is an observation by Hart 

 (Bull. Dept. Agr. Trinidad II., p. 155), who records 

 that Cathartes fastens used to collect in the morning 

 hours on trees near a plant of Aristolochia gigas v. 

 sturtevanti which was flowering, and which has a 

 particularly strong odour. There can be no doubt 

 that these birds have an efficient sense of smell. At 

 the same time I think that their congregation in 

 numbers is due to watching the movements of their 

 neighbours. C. B. Williams. 



Ministry of Agriculture, Cairo, Egypt, 

 June 29. 



The Skull of Sir Thomas Browne. 



1 1 may be known to some readers of Nature that 

 the skull of Sir Thomas Browne has recently been 

 reinterred at Norwich, but that previously it came 

 to London, where careful measurements, drawings, 

 and tracings of it were made. It is proposed to 

 publish a full account of the skull in Biometrika, but 

 it would add much to the interest of the proposed 

 monograph if it were accompanied by a series of 

 reproductions of the portraits and engravings of one 

 of the most noteworthy of Englishmen who have 

 combined the study of medicine with the pursuit 

 of literature. 



The large number of plates required to illustrate 

 adequately the relation of the skull to the portraits 

 renders — -under the present conditions of both printing 

 and illustrative work — the appearance of a complete 

 monograph, such as we desire to see issued, very 

 difficult. We propose, therefore, to issue one hun- 

 dred copies of the monograph at the price of one 

 guinea each, if lovers of Sir Thomas Browne can be 

 found in adequate numbers to subscribe for copies. 

 Will you kindly permit us to appeal through your 

 columns for the names of those who are willing to 

 aid in this scheme for putting on permanent record 

 the physical aspect of the author of the " Religio 

 medici," who, by that and his other works, has won 

 a unique position in the heart as well as in the mind 

 of every cultured Englishman ? Willingness to sub- 

 scribe may be notified to either of the undersigned 

 at the Royal College of Surgeons, Lincoln-Inn Fields, 

 and University College, London, respectively. 



Arthur Keith. 

 Karl Pearson. 



London, July 12. 



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