174 



NA TURE 



[February 15 1894 



ing type of mammalia, and we know nothing of the myriad 

 changes that have taken place during its evolution. Spencer 

 urges that Weismann has made no reply to the difficulty 

 of the distribution of tactile discriminativeness over the 

 skin. But even were it an established fact that the effects 

 of use are inherited, Mr. Spencer's suggestion would bring us \ 

 no nearer an explanation, as it cannot be supposed that increased 1 

 use would multiply the number of tactile end organs. If the ! 

 origin of the end organs be left unaccounted for, and it be said 

 that these changes in the brain that are the result of practice in 

 discrimination are accumulated by inheritance, still the argu- j 

 ment is not cogent. For a variation in the brain leading to the | 

 slightest increase of discrimination in interpreting the messages : 

 from the peripheral sense organs certainly have a value in j 

 selection. 



In the matter of Panmixia, Mr. Herbert Spencer has mis- 

 understood Weismann completely. Panmixia does not_ imply ! 

 selection of smaller varieties, but the cessation of the elimination , 

 of smaller or more imperfect varieties. The discussion of the | 

 variation of cooperative parts leaves the issues open. In the 

 case of the giraffe, Mr. Spencer thinks that the main points of j 

 its extraordinary structure must be due to natural selection. : 

 Nageli some time ago selected the case of the giraffe as a special 

 instance of the inadequacy of selection. But in the giraffe, and 1 

 in many other cases, as in the horns of a stag, increase of an 

 organ to be of any use must be accompanied by modifications 

 of a multitude of cooperating parts. For such cases of co- 

 adaptation, natural selection without the inherited results of 

 increased use, Mr. Spencer believes inadequate. Weismann's 

 chief reply is drawn from a study of neuter ants. In them 

 there are many structures different from the correspond- 

 ing structures in males and females, and of these some imply 

 the harmonious modification of cooperating parts. Follow- 

 ing those who have investigated ants most fully, Weismann 

 believes that most of these modifications arose subsequently 

 to the loss of reproductive power by workers and soldiers, 

 and that, consequently, we have here an instance of modifica- 

 tions involving coadaplation where there is no possibility of the 

 inheritance of acquired characters. Against this, Spencer has 

 set forth " certain views concerning the origin and economy of 

 social insects, which differ from those that are current." Ac- 

 cording to these views reproductive power was lost by neuters 

 subsequently to the appearance in them of the new characters, 

 and consequently upon his theory the inheritance of acquired 

 characters is not excluded. Thus, on his view the issues are 

 still open. 



When Mr. Spencer brought forward a set of instances sup- 

 porting the popular belief that offspring to a second sire occa- 

 sionally show traces of the first sire, he was apparently unaware 

 that Weismann had already discussed a number of such cases, 

 grouping them under the name " telegony."' In the famous case 

 of Lord Morton's mare it appears that the only resemblance to the 

 first sire was zebra-like stripes, and it has been known for very 

 long that such stripes not infrequently appear. Settegast and 

 Nathusius, two very great authorities on questions relating to the 

 breeding of animals, deny that there is proof of the existence of 

 telegony, and for the present at least it cannot be said that it forms 

 an argument against Weismann's theories. Moreover, the sug- 

 gestion made by Prof. Romanes, and accepted by Weismann, 

 provides an intelligible explanation of the hypothetical facts. 

 To anyone who has seen under the microscope the intricate 

 method in which nuclear matter prepares for division, Spencer's 

 suggestion that it passes from cell to cell, leaving the embryo and 

 reaching the tissues of the mother, must seem absurd, and his 

 comparison of the wanderings of microbes will not render his 

 supposition more intelligible. 



The discussions of the "immortality" of the Protozoa, and 

 of the exact meaning of division of labour, are largely academic, 

 and do not admit readily of being summarised. But it is clear 

 that unless generatio ccquivota be admitted, many existing Pro- 

 tozoa have been reproducing by simple division since at least 

 tertiary times, and that is a length of life certainly amounting to 

 the concept of "immortality" as used by Weismann. And if 

 there be a material basis of heredity at all (a view which 

 is by no means peculiar to Weismann), the material basis 

 whether it be called germ-plasm or not, and whether it be 

 modified in each ontogeny or not, stretches from animal to 

 animal since the beginning of things, and has a dower of life 

 immensely greater than the dower of life of somatic protoplasm. 



P. Chalmers Mitchell, 



ANCIENT EGYPTIAN PIGMENTS} 



'T'HE red pigment used by the Egyptians from the earliest times 

 -*■ is a native oxide of iron, a haematite. Most of the large 

 pieces found by Mr. Petrie are an oolitic basmatite. One spe- 

 cimen, on analysis, gave 7911 per cent, and another 81 '34 per 

 cent, of ferric oxide. The pieces to be used as pigments were no 

 doubt carefully selected, and the samples that I have examined, 

 mostly from Gurob and Kahun, are very good in colour. All the 

 large pieces were of a singular shape, having one side smooth and 

 curved ; and in all cases this side was strongly grooved with 

 striae, giving somewhat the appearance to the mass of its 

 having been melted, and allowed to cool in a circular vessel. 

 No doubt the explanation of this smooth-curved surface is, that 

 these pieces had actually been in part used to furnish pigments, 

 and having been rubbed with a little water in a large circular 

 vessel, had been ground to this shape. By experiment it was 

 found that these pieces of the native haematite yielded, without 

 any further addition by way of medium, a paint which could 

 readily be applied with a brush, as it possesses remarkable ad- 

 hesive properties, and it resembles exactly, in every particular, 

 the red used in the different kinds of Egyptian paintings. In 

 addition to these samples of the pigments, all of which are 

 native minerals and in their natural conditions, there are other 

 reds, finer in colour and smoother in texture, evidently a supe- 

 rior pigment ; these apparently have been made from carefully 

 selected pieces of haematite, which have been ground and 

 washed, and dried by exposure to the air. Some of these 

 pieces are very fine in colour, and it would be difficult to match 

 them with any native oxide of iron that is used as a pigment at 

 the present day. There is every reason to believe that this is 

 the earliest red pigment which was used, and it remains to this 

 day the commonest and most important one ; it is a body un- 

 attacked by acids, unchangeable by heat, and even moisture and 

 sunlight are unable to alter its colour. At the present time 

 many artificial products are used to take the place of this natural 

 pigment. 



Ycllotv Fig7nents. — These, again, are natural products, and 

 by far the most common yellow used by the Egyptians is a 

 native ochre. These ochres consist of about one-quarter of their 

 weight of oxide of iron, from 7 to 10 per cent, of water, and the 

 rest of their substance is clay. When moist they have a greasy 

 feel, and work smoothly and well with the brush. There is no 

 evidence of these bodies having changed colour, but undoubt- 

 edly they are chemically not nearly so stable as the red form of 

 oxide of iron. Many of the pieces of this pigment, found at 

 Gurob and at Tel-el-Armarna, are very fine in colour. 



Some of the specimens of the very earliest colours of which 

 the exact history is known, appear to be an artificial mixture of 

 these two colours, the red and yellow, thus producing an orange 

 colour. These samples were found on a tomb at Medum, 

 which, according to Prof. Flinders Petrie, was built by Nefer- 

 mat, a high official and remarkable man at the Court of Senefru. 

 Senefru is known to have lived in the fourth dynasty, about 

 4000 B.C. and to have preceded Khufu, the Cheops of the 

 Greeks, who was the great Pyramid builder. Now, on Nefer- 

 mat's tomb the characters and figures are incised and filled in 

 with coloured pastes, which I have been able to examine, and 

 it is of interest to know that this use of colour was a special 

 device of Nefermat, for on his tomb is stated that : " He made 

 this to his gods in his unspoilable writing." In this unspoil- 

 able writing the figures are all carefully undercut, so that the 

 coloured pastes, so long as they held together, should not be able 

 to drop out. All the pastes used are dull in colour, consisting 

 entirely of natural minerals. Haematite, ochre, malachite, car- 

 bon, and plaster of Paris appear to be the materials used. 

 Chessylite, as a blue, probably was known even at that date, 

 but the artificial blues seem hardly at this period to have come 

 into use ; certainly they are not found in the specimens of the 

 Nefermat colours which I have examined. Another yellow 

 pigment, far brighter in colour, was also often used. It 

 is a sulphide of arsenic, orpiment ; it is a bright and powerful 

 yellow, again a body found in nature, but a much rarer body 

 than ochre, and consequently, probably was only used for 

 special purposes, when a brilliant yellow was required. As far 

 as it is known at present, this pigment did not come into use 

 until the eighteenth dynasty. Gold might even be placed among 

 the yellow pigments, for it was largely used, and with wonder- 



1 A lecture delivered at the Royal Institution of Great Britain, on March 

 17, 1893, by Dr. William J. Russell, F.R.S 



NO. 1268, VOL. 49] 



