ao 



NA TURE 



[May lo, 1894 



haunted by it : and Mr. H. N. Dickson his charts and sections 

 showing the temperature of the water in the northern and 

 western parts of the North Sea and the Faroe- Shetland Channel 

 at all dejiths, August 1893. 



Dr. H. R. Mill and Mr. Edward Heawood exhibited bathy- 

 metrical maps of Windermere, I'llswater, Coniston Water, 

 Derwentwa'.er and Bassenthwaite, Buttermere and Crummock, 

 Ennerdale Water, Wastwater and Haweswater. Contour lines 

 at each 25'feet of depth beneath the surface were shown, and the 

 configuration of the basins was thus for the first time accurately 

 delineated. 



Prof. J. Norman Lockyer exhibited photographs of stellar 

 spectra taken with a 6-inch objective prism of 45', and photo- 

 graphs of the great sun-spot of February 1894, taken at Dehra 

 Dun. 



Living larvse influenced by the colours of their surroundings 

 were exhibited by Prof. E. B. Poulton ; and microscopic slides 

 illustrating the behaviour of the nucleus during spore formation 

 in the hepatica-, by Prof. 1. B. Farmer. 



Photographs of diffraction and allied phenomena were ex- 

 hibited by Nfr. W. B. Croft. The photographs showed Newton's 

 rings, reflected and transmitted ; Grimaldi's fringes ; Fresnel's 

 interference from a bi-prism ; Arago's shifting of bands to- 

 wards the denser medium ; Talbot's bands. The shadows of 

 needles, wire gauze, perforated zinc, a screen with circular 

 holes, opaque circular screens with Arago's bright centre. A 

 comparison of the diffraction of Fresnel with that of Fraun- 

 hofer and Schwerd ; the diflfracting ob'ect consists of groups of 

 small circles of light. Uniaxal and biaxal crystals ; conical 

 refraction. 



Specimens demonstrating some phenomena of chemiotaxis in 

 inflammation were exhibited by Mr. W. B. Hardy and Dr. 

 A. A. Kanthack. 



Prof. Marshall Ward showed apparatus employed for 

 observing and measuring the growth of bacteria, fungi, and 

 other micro-organisms under diflferent conditions under the 

 microscope. The essential feature is the culture-cell. It has a 

 quartz floor, and is capable of holding large quantities of water, 

 and thus while letting the light-rays pass does not rapidly vary 

 in temperature. By the side of the culture-cell containing the 

 hanging-drop in which is the organism under observation, is an 

 exactly similar cell, but with a small thermometer in it, the 

 blackened bulb of which is in the cell, andigives the temperature 

 inside the latter. The rest of the apparatus consists in the 

 measuring eyepiece ; the screens of coloured glass, various 

 liquids, &c., for growth indifTcrent kinds of light ; and a warm 

 chamber in which the whole microscope can be enclosed and 

 kept at known temperature. 



A demonstration of the trails of Oscillatorise formed the 

 exhibit of Mr. J. G. Grenfell. 



Prof. E. Waymouth Reid exhibited microscopic specimens 

 illustrative of the process of secretion in the skin of the eel. 

 The chief point of general interest in the process is the peculiar 

 manner in which the surface of the skin is cast off when the 

 animal is stimulated. 



Prof. G. B. Howes exhibited eggs and young of Ceratodus 

 Fot ileri, and a male of Ltpidoiirtn paradoxa. 



Mr. E. J. .Mien showed nerve elements from the ganglia of 

 lobster embryos ; and Dr D. Sharp a collection of while ants 

 Termitida). 



A specimen and drawing of the South American mud-fish, 

 Ltfidosirin paradoxa, was exhibited by Prof. E. Ray Lankcsler. 

 See Nature, vol. xlix p. 555.) 



_ Dr. Alexander Muirhead exhibited a new form of Lord 

 Kelvin's siphon recorder, Muirhead's artificial cable, and Muir- 

 head s automatic curb transmitter. Lord Kelvin's siphon 

 rcc rilcr and Muirhead's automatic curb transmitter were shown 

 in ..[cration in connection with an artificial cable of the same 

 c.ip.icily and conductor resistance as the .Vll.inlic cable, which 

 is to be laid next July by the Anglo-American Telegraph Com- 

 pany. Capaciiy of artificial cable 800 microfarads ; resistance 

 of conductor 3350 It. .\. units. 



T'cmonstrations l.y meant of the electric lantern took place 

 during the evening, I>r. D. H. Scott showing photographs 

 from sections in Dr. W C. Williamson's collection, illu.strat- 

 ing the microscopic structure of fossil plants from the coal- 

 meaiares. The lantern was also used by Prof. K. B. 

 Poallon, who exhibited illustrations of recent work upon 

 the influence of environment upon the colours of certain 

 Lepidopterous larv.T. Variously coloured twigs and shoots, 



NO. I 280, VOL. 50] 



such as occur in nature, have been .shown to influence the 

 appearance of many twig-like larvas in such a manner as to con- 

 ceal them. Duiingthe summer of 1893 certain larvae of two 

 species (Gastrnpacha quercifolia and Otontoptera bidcntatd^ 

 were surrounded, during their growth, with lichen-covered 

 twigs. Larvx thus treated developed lichen-like marks upon 

 the bod). 



THE RELA TIVE SENSITIVITY OF MEN AND 

 WOMEN AT THE NAPE OF THE NECK 

 (BV WEBER'S TEST). 



'T'HE difference in the sensitivity of the two sexes has been 

 discussed often and from various points of view, but still, 

 as it would seem, upon insufficient data. More observations 

 being wanted, I submit the following, partly for such 

 value as they have in themselves, parily to show an easy 

 method of observation which others may pursue with advan- 

 tage, and partly as a good illustration of the method of per- 

 centiles, or centiles. 



The test employed is one of a familiar kind, made with the 

 pnints of a pair of compasses, and usually associated with the 

 name of Weber. If one person becomes just conscious of the 

 doubleness of the pricks when the distance between the points 

 is a, and another person does so when the interval is i>, then 

 the ratio of a to i> may fairly be taken to express the relative 

 obtuseness of the two persons, so far as concerns the form of 

 sensitivity tested, and the inverse ratio of /' to a to represent 

 its relative delicacy. The particular test used was one 

 that has three especial merits : it requires no minuteness of 

 measurement, no uncovering, and the person tested is unable 

 to see the operation. It consists in pressing the points of the 

 compasses against the nape of the neck .ind across the line of 

 the spine, while the experimenlee sits with his or her head 

 bowed forward. The just-perceptible interval at the nape of 

 the neck averages as much as half an inch or thereabouts, 

 while its variation in different persons is large. Consequently 

 there is no need for extreme delicacy of measurement, neither 

 does the varying thickness of cuticle caused by various degrees of 

 usage, interfere materially with the results, as it does when like 

 experiments are made, as is usual, on the finger-tips. The 

 varying delicacy of perception due to difl'ering amounts of 

 practice is here entirely eliminated, because all persons are 

 equally unpractised, no one occupying himself or herself in 

 attempts to discriminate between two simultaneous pressures 

 on the nape of his or her neck, while everybody has life-long 

 practice in discriminating roughnesses, thi ugh in various and 

 unascertainable degrees, with his or her fingertips. There are 

 parts of the body, such as the back, which are still less dis- 

 criminative than the nape of the neck, but there is no other 

 equally suitable part that is so get-at-able, in respect to the 

 the ordinary dress of man or woman Lastly, the attitude of 

 the person who is being tested, entirely precludes him from 

 watching the operator, and guessing Irom the hands or move- 

 ments ofthe latter, whether he is applying two points, or only 

 one, at the moment when he asks what is (elt. The observations 

 were all made by .Sergeant Randall, who superintends my 

 laboratory ; he employed the two points of a Flower's ciani- 

 ometcr, which was handy for use, as it was wanted to make 

 other measurements of the same persons. The observations 

 were carried on for some months, until a suflicient number had 

 accumulated lo justify discussion. Stature was included among 

 them, but, failing on examination to trace any notable relation 

 between stature and the just-perceptible interval on the nape of 

 the neck, I have disregarded stature altogether in the following 

 summary, and age too, so far that the person tested was often 

 not fully grown. 



The observations made on males and females, reipectively, 

 arc summarised in the first and third lines of Table I. Their 

 sums, reckoned in each case from the beginning of the series, 

 are entered in lines 2 and 4, while the percentages of those 

 sums are given in lines 3 and 6, but .solely for the purpose of 

 graphic projection in the form of dots, in Fig. I. Those dots 

 are joined by straight lines, forming traces for the males and 

 females respectively. The lengths ofthe ordinates to the traces, 

 which are drawn at the lOlh, 20ih, &c. divisions of the b.ise, 

 are the loth, 20lh, &:c. percentiles, or centiles; or, in still 

 briefer language, the Isl, 2nd, &c. "deciles." Their values, 

 obtained by simple interpolation from the entries in lines> 



