April II, 1872] 



NATURE 



463 



Protective Mimicry 



In Nature, No. 126, for 28th ult., at p. 436, M. G. Pouchet 

 is recorded to have stated in a paper read before tlie Academy 

 of Sciences, first, ihat prawns accommodate their colour to that 

 of surrounding objects ; second, that removing their eyes pre- 

 vents tills change of colour. 



Of the truth of the first assertion I presume there is no doubt ; 

 but of the second I should much like to learn further, for when 

 we speak of Protective Mimicry in all the lower forms of life, 

 we do not assume that there is any ratiocinative mimicry. Yet 

 if this power of protective mimicking in the prawn is dependent 

 upon eye-sight, i.e., upon the power of conveying impressions 

 upon the optic nerve to the brain, does it not cease to be 

 "mimiciy " as generally understood, and pass into the order of 

 mental volition ? If so, how vast and interesting is the con- 

 sideration ! 



I hope that Mr Darwin, Mr. Wallace, or some other of your 

 scientific contributors will enlighten through your columns 



March ji _ Ignoramus 



CRANIAL MEASUREMENTS 



■^1 rH I LE engaged in the investigation of another matter, 

 ' * I was induced to make a series of cranial mea- 

 surements, and these I wish to record under the impres- 

 sion that they may be of use in the hands of some future 

 worker, though by themselves they are not of much value. 



The measurements were made at Wakefield, in York- 

 shire, during lS68-g, and are those of the working-classes 

 of the town and neighbourhood. Careful inquiry was 

 made as to the bathplace and parentage of each subject, 

 and no measurements are given save of those belonging to 

 the basin of the ! ivers Calder and Aire. The type of the 

 people is pre-eminently Saxon, and the results may there- 

 fore be taken as pretty accurately representing the con- 

 figuration ol^ the crania of modern Yorkshire. 



Attached are also the average height and weight for 

 each decade, and a calculation of the average cephalic 

 index. 



The measiirem"nts of the head were taken by large cal- 

 lipers, and aresii,:ply the greatest bi-parietal and occipito- 

 frontal diameters, and the measurement of the face is from 

 the tip of the chin to the root of the hair on the forehead. 



The average cephalic indices of the whole would show 

 men to be slightly more brachio-cephalic than women (by 

 ■75), while the result of the whole is decidedly eur>'cephalic. 



The cephalic indices of each decade of age would lead us 

 to believe that dolicho-cephalic people have a better chance 

 of life than the brachio-cephalic people, unless we believe 

 that the form of the cranium alters between thirty and 

 forty years of age. 



The entire table leads me to believe that there is not 

 much value to be placed in such cranial measurements for 

 the purposes of racial distinction ; certainly not in isolated 

 skulls ; for see the curious variations of measurement in 

 ■couples of the same sex taken from the same decade, as 

 shown in the table below : — 



For the purpose of contrasting the results I have 

 obtained in the measurements of height and weight, I 

 add a translation of Quetelet's tables : — 



