July 14, 19 10] 



NATURE 



61 



of the application of the method to (i) a leaf of Prunus 

 Laitrocerasus ; {2) the blood and tissues of a cat after 

 death by a known amount of HCN ; (3) the blood and 

 tissues of a person " found dead." — Prof. A. Dendy : 

 The structure, development, and morphological interpreta- 

 tion of the pineal organs and adjacent parts of the brain 

 in the tuatara (Sphenodon punctatus). The " pineal com- 

 plex " consists of the dorsal sac, the paraphysis, the pineal 

 sac (" epiphysis "), the pineal eye, the pineal nerves and 

 their central connections. There is a well-developed 

 choroid ple.xus, with special blood-supply, on the roof of 

 the dorsal sac, possessing histological features of consider- 

 able interest. The paraphysis is a compound tubular 

 gland, with special blood-supply, differing markedly in 

 histological character from the choroid plexuses. Its lining 

 epithelium forms a syncytium, and its opening, which, in 

 the embryo, lies just in front of the commissura aberrans, 

 becomes shifted upwards in the adult on to the anterior 

 wall of the dorsal sac, by the formation of a " supra- 

 commissural canal," the original opening being blocked up 

 by the anterior choroidal blood-vessels. The histological 

 structure of the pineal sac points to a sensory rather than 

 a glandular function. Its wall is essentially similar in 

 structure to the retina of the pineal eye, consisting of 

 radial supporting fibres, sense-cells, and ganglion-cells and 

 nerve-fibres, and pigment may occasionally be deposited 

 in it. The retina of the pineal eye consists of the same 

 histological elements arranged in essentially the same way, 

 with the sense-cells on the inside and the nervous elements 

 in the middle. The pigment is not lodged either in the 

 sense-cells or in the supporting fibres, but is brought into 

 the retina by wandering pigment-cells. The pigment 

 granules escape from these wandering cells on entering the 

 retina, and stream inwards between the radially arranged 

 elements. The inner ends of the sense-cells project into 

 the cavity of the eye, and are covered each by a little 

 cap, formed apparently by the internal limiting membrane 

 of the retina. The developing lens of the pineal eye 

 increases in size partly as a result of mitotic divisions in 

 a marginal zone of undifferentiated cells. As they approach 

 the centre the cells elongate, and some of them degenerate 

 into a kind of mucus, which is secreted from the inner 

 surface of the lens into the cavit/ of the eye, w'here it 

 takes part in the formation of the vitreous body. This 

 process of secretion continues in the adult. The nerve of 

 the pineal sac is from its first appearance median. It 

 joins the roof of the brain between the posterior and 

 superior commissures. The nerve of the pineal eye is 

 shown, especially by its development, to be primarily con- 

 nected with the left habenular ganglion, which even in 

 the adult has a different shape from that of its fellow of 

 the opposite side. Both nerves persist in a well-developed 

 condition throughout life. The view that the pineal sac 

 and pineal eye are respectively the right and left members 

 of a primitive pair of sense-organs, serially homologous 

 with the lateral eyes, is strongly supported. Altogether six 

 pairs of diverticula are given off from the fore- and mid- 

 brain, viz. the cerebral hemispheres, the optic vesicles of 

 the lateral eyes, the recessus thalami prenucleares, the 

 pineal sense-organs, the recessus geniculi, and the optic 

 lobes. These may all be serially homologous with one 

 another, and each may possibly indicate a separate neuro- 

 mere. There is no commissura mollis and no unpaired 

 plexus medianus in the third ventricle. Reissner's fibre 

 and the sub-commissural organ are very well developed. — 

 J. A. Crowther : The scattering of homogeneous $ rays, 

 and the number of electrons in the atom, (i) The scatter- 

 ing of a homogeneous pencil of $ rays has been measured 

 for various substances and for rays of different velocity. 

 It has been shown to obey the following statistical laws : — 

 (i) for rays of given velocity the intensity I of the radia- 

 tion contained within a given cone may be expressed by 

 the equation I/I„=i — c~'", where t is the thickness of 

 material passed through, and k a constant depending upon 

 the angle of the cone ; (ii) for rays of given velocity the 

 most probable angle of emergence is proportional to the 

 square root of the thickness of material traversed by the 

 rays : (iii) for rays of different velocities, the probable angle 

 of emergence divided by the square root of the thickness 

 traversed is inversely proportional to the product of the 

 mas? of the incident /3 particle into the square of its 



NO. 2124, VOL. 84] 



velocity. (2) From equations given by Sir J. J. Thomson, 

 the number of electrons contained in atoms of different 

 elements is deduced. It is thus found : — (i) that the ratio 

 of the number of electrons per atom to the atomic weight 

 is constant, the ratio being very nearly 3-0 for all the 

 elements examined ; (ii) that the positive electricity within 

 the atom is not in an electronic condition, but is distributed 

 fairly uniformly over the space occupied by the atom. 

 (3) Experiments are described on the absorption of homo- 

 geneous 3 rays. It is shown that the first stage in the 

 absorption of a pencil of homogeneous P rays consists in 

 the scattering of the rays according to the laws already 

 considered. The absorption of the completely scattered 

 radiation is then shown to take place according to an 

 exponential law. — F. Isaac : The spontaneous crystallisa- 

 tion and the melting- and freezing-point curves of mixtures 

 of two substances which form mixed crystals and possess 

 a minimum or eutectic freezing point. — Mixtures of azo- 

 benzene and benzylaniline. The results obtained in this 

 research may be thus summarised : — (i) The freezing- and 

 melting-point curves for mixtures of azobenzene and benzyl- 

 aniline have been determined, and it has been shown that 

 these substances possess a minimum or eutectic point at 

 26° for the mi.xture containing 19 per cent, azobenzene 

 and 81 per cent, benzylaniline, and form a series of mixed 

 crystals on one side only of the eutectic, viz. that with 

 excess of azobenzene. This is, therefore, a limiting case 

 of Roozeboom's Type 5, in which two substances, A and 

 B, possess freezing- and melting-point curves which exhibit 

 a minimum eutectic point, and form two series of mixed 

 crystals, i.e. mixed crystals containing excess of A, and 

 mixed crystals containing excess of B. (2) The melting- 

 point curve has been confirmed by actual analysis of the 

 mixed crystals. (3) The supersolubility curve, or curve of 

 spontaneous crystallisation, has been determined for these 

 mixtures by two methods : — (i) by noting the temperature 

 at which a liquid mixture of known composition crystallises 

 spontaneously in a sealed tube ; (ii) by noting the tempera- 

 ture at which a known liquid mixture attains its highest 

 refractive index and gives a dense labile shower when 

 placed in the trough of the inverted goniometer. It has 

 been shown that each mixture possesses a definite tempera- 

 ture of spontaneous crystallisation. The supersolubility 

 curve shows a minimum for liquids having approximately 

 the eutectic composition, and runs approximately parallel 

 to the freezing-point curve. It crosses the melting-point 

 curve three times. The nature of the mixed crystals which 

 first separate spontaneously from any liquid mixture on 

 the supersolubility curve has been investigated. The com- 

 position of such crystals has been determined by separating 

 them from their mother liquor and finding their melting 

 points. (5) A few thin sections have been ground from 

 the solid mixtures in the neighbourhood of the eutectic, 

 and their structures examined. These structures do not 

 appear to be permanent. After the lapse of some months 

 they completely changed, new crystal needles appearing all 

 over the sections. These changes, however, appear to be 

 very gradual, and to take place with change of tempera- 

 ture. — E. C. Snow : The determination of the chief corre- 

 lations between collaterals in the case of a simple 

 Mendelian population mating at random. This paper 

 investigates the values which should hold for the correla- 

 tions between (a) siblings, (b) uncle and nephew, and (c) 

 first cousins, on the Mendelian hypothesis of " unit- 

 characters." The correlations both for gametic and 

 somatic characters are found. For the former, values in- 

 dependent of the distribution of the dominant and recedant 

 characters among the population are obtained. These are 

 (a) o-soo, (b) 0-250, and (c) 0250. In the case of the 

 somatic correlations, however, the results depend upon the 

 relative numbers of the population possessing the dominant 

 and recedant attributes before crossing. By varying this 

 proportion, different values of the correlations can he 

 obtained, but these are always less than the corresponding 

 gametic ones stated above. .The investigation brings out 

 the important point that, on the Mendelian theory of 

 heredity, the similarity between first cousins is quite as 

 close as, or closer than, those between uncle and nephew. 

 Biometric results previously reached have pointed to the 

 same conclusions. This is of great interest from the 

 medical point of view. In medical diagnosis, a man's 



