;28 



NATURE 



[May 12, 1910 



examination of the forms of that species found in Egypt. 

 The author pointed out that on examination of the hind- 

 foot measurements of a considerable number he found 

 tnat the curve showed three distinct apices, and that two 

 of these apices belonged, respectively, to the two forms 

 found in Egypt, these forms being also more easily dis- 

 tinguished by their colour characteristics. The author in 

 dealing with the rats of this species from the Oriental 

 region had some years ago subdivided them into three sub- 

 groups, and it was now shown that the size of the feet 

 typical of the three Oriental subgroups corresponded with 

 the three apices in the curve of the Egyptian forms. He 

 was inclined to think that these apices represented centres 

 of variation, and were probably inherited as Mendelian 

 characters, for were this not the case the smallest apex 

 would have become swamped, and a regular curve would 

 result. It was, however, evident that the small foot 

 character was present and ready to become the dominant 

 form in a very short time should conditions giving 

 advantage to a small foot arise. On comparing the curve 

 of the hind feet of Mus norvegictts, three apices were also 

 observed, showing that in this species the " hind-foot 

 character " was also present, but as there were no corre- 

 sponding colour differences it was impossible to tell to 

 which group any particular individual belonged. The 

 author drew the following conclusion, viz. that there was 

 considerable prima facie evidence that the size of the hind 

 foot and the colour of the hairs on the underparts were 

 Mendelian characters, and pointed out that the former 

 character was also found in another species, Mus 

 norvegicus, and the latter in a third species, Mus musculus. 

 — G. E. Bulien : An example of posterior dichotomy in 

 an Aylesbury duckling. A detailed account of a dissection 

 performed on a duckling having supernumerary legs. In 

 addition to a re-duplicated pelvis and the usual condition 

 of the limbs presented in posterior dichotomy, it was found 

 that the specimen showed evidence of a further re-duplica- 

 tion of the part dichotomised. 



Roval Microscopical Society, Apr 20 — Mr. E. J. 

 Spitta in the chair. — E. M. Nelson : What did our fore- 

 fathers see in a microscope? The author dealt with the 

 subject of what sort of image would be seen in a micro- 

 scope of the highest type before 1825, about which date 

 the achromatising of objectives was begun. After describ- 

 ing various old forms of microscope, particularly Dr. Robt. 

 Smith's catadioptric microscope, the author gave examples 

 with modern instruments.- — E. M. Nelson : Critical micro- 

 scopy. The author described the image of an object as being 

 critical when it had been obtained by means of an objective 

 of fine quality which had been placed in correct adjustment 

 for that object, and when the illumination was critical. 

 An object was said to be illuminated critically when it was 

 placed at the apex of a solid axial cone, the aperture of 

 which was not less than three-quarters of the N.A. of the 

 objective. 



Institution of Mining and Metallurgy, April 21. — 

 Mr. Edgar Taylor, president, in the chair. — W. 

 McDermott : The elements of slime concentration. In 

 this paper the author gave a brief review of certain factors 

 in the problem of slime concentration which seem to be 

 established by practice, "and then proceeded to draw con- 

 clusions from that review which would show the lines on 

 which inventive and constructive development should pro- 

 ceed. He made a broad classification of the types of 

 machine in use into five groups having different functions, 

 and from that went on to analyse the conditions essential 

 to efficiency, these teing, respectively, time required for 

 settling, smoothness of surface in final separation, speed 

 of the washing water, and the special shaking motion 

 necessary for settling and separation. Following these 

 points was a consideration of the direction likely to be 

 taken in future improvements, which may or may not 

 provide for the production of a middle product, while the 

 desirability or otherwise of classification under commercial 

 conditions also received notice. — ^J. M. Campbell : The 

 origin of laterite. The author dealt more especially with 

 occurrences of laterite in West .Africa, which he had 

 observed and studied, though he sought to establish a 

 similarity of origin for the Indian laterites, also in con- 



NO. 2 1 15, VOL. 83] 



tradiction to the generally accepted theories of the Geo- 

 logical Survey of India. His definition was, briefly, to 

 the effect that laterite is a porous rock, formed above low 

 water-level in the strata on low-lying gentle slopes, by 

 the gradual removal of some or most of the mineral con- 

 stituents of either alluvium or rock in situ, and of the 

 deposition therein of ferric and aluminous hydrates from 

 mineralised water coming from below, the deposition 

 being determined by contact with atmospheric oxygen. — 

 J. M. Campbell : Native iron smelting in Haute Guinde 

 (West Africa). This is a brief note compiled from 

 observations of some native furnaces which are probably 

 survivals of an ancient system of iron smelting, no record 

 of which appears to exist. Their chief interest consists 

 in the method of operation by natural draught only, in- 

 duced by the introduction of clay tuyers, which convey air 

 to the combustible matter, so dispensing with artificial 

 blast. The note is of historical interest only, as the - 

 method of smelting is now almost extinct. — H. B. J 

 Williams : Hammer drills in overhand stoping and * 

 raising. In this paper the author gives particulars of the 

 construction, operation, and work performed by a hammer 

 drill operated by compressed air, which has been in prac- 

 tical use for some time in some gold mines in British 

 Columbia, and has shown some distinct advantage over , 

 hand labour and ordinary piston drills in certain classes 

 of work. 



Challenger Society, April 27. — Dr. A. E. Shipley in the 

 chair. — A. Earland : The Foraminifera collected by the 

 fisher}' cruiser Goldseeker, with special reference to the 

 survival of boreal species in a southern locality. These 

 Foraminifera had been dredged in the area of the Moray 

 Firth and North Sea to the east of Scotland as far north 

 as the extremity of Shetland, and eastwards to about 150 

 miles from the Scottish coast. Off Buchan Ness large and 

 typical specimens of Polystomella arctica, P. and J., were 

 obtained. In the deep " gully " off Burghead, Moray 

 Firth, Botellina labyrinthica, Brady, was found in abund- 

 ance, and Hippocrepina indivisa, Parker, a truly Arctic 

 type, was frequent. From these records, and from the: 

 gigantic size attained by many arenaceous types in the 

 comparatively shallow water of the central North Sea, the 

 author considered that the present rhizopod fauna of the 

 North Sea was of Arctic origin, surviving from the com- 

 paratively recent geological times when the North Sea had 

 no connection with the Atlantic in the south. The 

 immigration of warm-water types by way of the north of 

 Scotland was regarded as further proof of the correctness 

 of the geological theory, and many instances of such 

 rhizopod types occurring in the northern area of the Moray 

 Firth, but nowhere south of it, were mentioned. 



Geological Society. April 27. — Prof. W W. Waits, 

 F.R.S., president, in the chair. — R. G. Carruthers : The 



evolution of Zaphrentis delanouei in Lower Carboniferous 

 times. The simple corals that belong to the gens of 

 Zaphrentis delanouei are of common occurrence in the: 

 Lower Carboniferous rocks of Scotland. Their distributiort 

 is sporadic, but it is possible to collect over areas of which 

 the stratigraphy is known. Many specimens have been got 

 together from horizons scattered throughout the sequence. 

 The ontogeny has been investigated by serial transverse 

 sections. The evolutionary changes observed are confined: 

 to the disposition of the septa, which has influenced the- 

 shape of the cardinal fossula in a marked manner. | 

 Zaphrentis delanouei is typically a Tournaisian species,- 

 and it has a wide fossula, expanded inwardly. When the 

 gens first appears in the Scottish rocks Z. delanouei is' 

 the predominant form, but is associated with a mutatior^' 

 in which the fossula is parallel-sided. In the higher lime-' 

 stones of Lawston Linn another mutation appears, which 

 is regarded as a sport from the direct line. In the succeed- 

 ing Lower Limestone group the gens undergoes further 

 modification. Adults of the two Cementstpne species are 

 extremely rare, and the predominant form has a fossula 

 which narrows rapidly to the inner end. In the still 

 higher horizons of the Upper Limestone group the last 

 mentioned mutation becomes predominant, and persists u 

 to the Millstone Grit, where the septa become mor 



