September 27, 1906J 



NA TURE 



553 



likely to survive and to perpetuate dark forms. Mr. 

 Porritt did not believe that birds fed to any great extent 

 on moths, and when they did they took them on the wing 

 at night, when their colour similarity to trees would be 

 of no service. Moreover, many melanic species do not 

 affect tree trunks, e.g. Larentia multistrigaria, in which 

 melanism has rapidly developed for no apparent reason. 

 The theory that smoke and humidity in the manufacturing 

 districts have caused melanism, although offering in many 

 cases a likely explanation, seems to be rendered untenable 

 by numerous exceptions. Mr. Doncaster remarked that 

 melanism could not be explained as due to natural selec- 

 tion or as the result of external conditions, as the black 

 forms in some cases arose suddenly, and quickly became 

 numerous. The black form is dominant, that is, the off- 

 spring of a pair, one black and one pale, have a tendency 

 to be dark. Dr. Dixey pointed out that in Pierines dark 

 pigment is often substituted for light, the female being 

 usually darker. There may even be two grades of colour 

 in the females, a darker in the individuals found in the 

 wet season, and a lighter in those found in the dry season. 

 He considered that locality, altitude, and other conditions 

 may have an influence in darkening the pigment. 



Pineal Eye of Gcotria and Sphcnodon. 

 Prof. Dendy described the structure of the pineal eye 

 of the New Zealand lamprey (Geotria), which agrees in 

 most respects with that of Petromyzon, but the former is 

 more complex in histological structure, its pigment cells 

 being divided into inner and outer segments. The pineal 

 nerve is connected both with the right habenular ganglion 

 and the posterior commissure, and in all probability with 

 Reissner's fibre, whereby it would become linked with the 

 optic reflex apparatus described by Sargent. Prof. Dendy 

 also directed attention to some newly observed details of 

 structure in the adult pineal eye of Sphenodon. The rods of 

 the retina project into the cavity of the eye, and are con- 

 nected with a network of fibres, which is also connected 

 with the "lens." The lens contains a large central 

 cell which resembles a unipolar ganglion cell. Prof. Dendy 

 concluded that, in both Geotria and Sphenodon, the pineal 

 eye is a functional organ. 



Formation of Nucleoli. 

 Prof. Havet (Louvain) traced the formation of true 

 nucleoli or plasmosomes in the nerve cells and blood cells 

 of Rana and Alytes. The central part of each is formed 

 from a small, clear area situated in the centre of the 

 telophasic figure, while the peripheral part is derived from 

 the internal extremities of the chromosomes which remain 

 when the rest of the chromosomes form the nuclear net- 

 work. Occasionally chromosomes also become included in 

 the central area, giving rise there to one or two chromatic 

 structures. 



Milk Dentition of the rrimitive Elephant. 

 Dr. C. W. Andrevi's, in the course of a paper on the 

 milk dentition of the primitive elephant, pointed out that 

 in recent elephants, owing to the large size of the molars 

 and the shortening of the jaws, the teeth have an almost 

 horizontal succession, their manner of replacement differing 

 widely from the vertical succession found in other mammals. 

 But as the earlier relatives of the elephant are followed 

 back through the various Tertiary horizons a gradual 

 approximation to the ordinary mammalian type of tooth 

 replacement is observed, until in the recently discovered 

 Eocene Palsomastodon a form is reached in which the 

 milk molars are replaced in the normal way by premolars, 

 which, along with the permanent molars, remain in use 

 throughout the life of the animal. 



A New Conception of Segregation. 

 Mr. A. D. Darbishire directed attention to some essential 

 but usually unrecognised features of the Mendelian theory. 

 He pointed out that although half the total number of 

 children born to hybrids were unlike their parents, the 

 hybrids, according to that theory, bore no single germ 

 cell containing an element representing an animal like 

 themselves, and that if a hybrid could be made to multiply 



NO. 1926, VOL. 74] 



parthenogenetically it would produce no offspring like 

 itself. An experiment for testing this theory in an in- 

 dividual case was described. 



Mr. J. T. Cunningham spoke on the evolution of the 

 cock's comb; Mr. H. M. Bernard, on a periodic law in 

 organic evolution, with a re-estimation of the cell ; and 

 Dr. H. J. Fleure and Miss Galloway gave a detailed paper 

 on the habits of the Galatheidjc in relation to their struc- 

 ture ; but these and a few other papers do not lend them- 

 selves to the purposes of a summary. 



J. H. AsilWORTH. 



THE ROYAL I'llOTOGRAPHlC .SOCIETY'S 

 ANNUAL EXHIBITION. 

 'T'HIS exhibition at the New Gallery in Regent Street 

 •*• will remain open until October 27. The three rooms, 

 the central court, and the balcony, indicate its five main 

 divisions. The last of these is devoted to scientific and 

 technical photography and its application to processes of 

 reproduction, and the exhibits here naturally fall into three 

 sections, namely, the ordinary exhibits, those contributed 

 by special invitation of the council of the society, and a 

 small collection of photographs that have no other interest 

 than that they are good technical work, and represent 

 subjects of more or less interest, chiefly architectural. 

 We hope to see this kind of work more fully represented 

 in future e.xhibitions, for between the more strictly tech- 

 nical and the ultra-pictorial it has been almost squeezed 

 out of existence. 



A series of beautifully made models of light-pencils, 

 which show the various effects of aberrations that par- 

 ticularly concern photographic lenses, is shown by Mr. 

 C. Welborne Piper, and has been awarded a medal. The 

 three dozen models illustrate very clearly a subject that 

 must always be a somewhat difficult one. Immediately 

 following this are a large number of photographs of living 

 things, but chiefly birds, which appear to be receiving a 

 very undue share of attention just now. Of these, we 

 notice particularly a series of twenty-four photographs of 

 the stone curlew in different stages of its existence, by Mr. 

 W. Farren. Of the other subjects, " A Study of Wych 

 Elms," by Mr. Alfred W. Dennis, is among the more novel. 

 It is a series of seven photographs that show the same 

 pair of trees, leafless and in leaf, and on larger scales the 

 details of the trunk, blossom, fruit, leaves, and winter 

 buds. Dr. Vaughan Cornish sends a further series of 

 waves ; Mr. J. C. Burrow two coal-mine subjects, excel- 

 lently rendered as usual ; and Mr. Bagot Molesworth a 

 telephotograph of Vesuvius in eruption, taken from a 

 distance of eight miles. 



In the invitation section, Mr. Douglas English shows 

 some examples of mimicry in British insects, and a par- 

 ticularly realistic effect is obtained in some of them by 

 making the original carbon print with a green tissue, and 

 staining the insects with dyes to represent their natural 

 colours. The Royal Observatory, Greenwich, has con- 

 tributed several of its recent results, including some of 

 last year's solar eclipse. Mr. F. E. Baxandall (for Sir 

 Norman Lockyer) also illustrates the eclipse, and sends 

 photographs of two British stone circles that were erected 

 some four thousand years ago as astronomical observ- 

 atories. Series of cloud photographs are shown by Dr. 

 \V. J. S. Lockyer and Captain D. Wilson-Barker. Photo- 

 graphs illustrating the investigation of crimes, such as 

 forgery and burglary, and the detection of the criminals, 

 by Prof. R. A. Reiss, of Lausanne, will be of very 

 general interest. Mr. K. J. Tarrant shows a series of 

 thirty photographs of high-tension electrical discharges. 

 Mr. Edgar Senior has continued his study of the Lipp- 

 mann method of colour photography, and although the 

 image generally shows no grain under the microscope, he 

 has by special illumination got the surface to appear 

 covered with discs of light, though what these indicate is 

 not very clear. 



There are a few photographs in " natural colours," but 

 nothing better than, if quite so good as, has already been 

 shown. Messrs. Sanger-Shepherd and Co., by preparing a 

 more rapid and red-sensitive plate and special colour filters. 



