Aug. lo, 1876] 



NATURE 



309 



transparent, as thoujjh the hand were seen through it. This 

 experiment is not new, but I have never seen it described. The 

 explanation of it is quite evident. 



2. Drop a blot of ink upon the palm of the hand, at the 

 point where the hole appears to be, and again observe as before. 

 Unless the attention be strongly concentrated upon objects seen 

 through the tube, the ink-spot will be visible within the tube 

 (apparently), but that part of the hand upon which it rests will 

 be mvisible, unless special attention be directed to the hand. 

 Ordinarily the spot will appear opaque. By directing the tube 

 upon brilliantly illuminated objects, it will, however, appear 

 transparent, and may be made to disappear by proper effort. By 

 concentrating the attention upon the hand, it may also be seen 

 within the tube (especially if strongly illuminated), that part 

 immediately surrounding the ink>spot appearing first. 



3. Substitute for the hand a sheet of unruled paper, and for 

 the ink-spot a small hole cut through the paper. The small 

 hole will appear within the tube, distinguishing itself by its 

 higher illumination, the paper immediately surrounding it being 

 invisible. Many other curious experiments will suggest them- 

 selves. For example : if an ink-spot somewhat larger than the 

 tube be observed, the lower end of the tube will a;ppear to be 

 blackened on the inside. 



4. While making these experiments, an improvement upon 

 the experiment described in Nature, vol. xii., p. 502, was 

 suggested, as follows : — Look through a paper tube with one 

 eye at green paper, and through another tube with the other eye, 

 at red paper. The paper should be illuminated by the direct 

 solar ray. The two colours, at first vivid, are rapidly enfeebled. 

 After half a minute, transfer both eyes to either one of the 

 papers, say red. To the eye fatigued by green, the red colour is 

 very brilliant, and the effect is the more striking on account of 

 the simultaneous impressions now received by the two eyes. 



Washington University, St. Louis 



F. E. NiPHER 



Antedated Books 



The evil practice of issuing antedated periodicals has long 

 been a matter of complaint amongst naturalists. The editor of 

 the ^Journal Jiir Ornithologie is a well-known sinner in this 

 respect — the quarterly number of that journal, although in- 

 variably dated on the first day of each quarter, being always 

 several months in arrear. But a still more flagrant instance of 

 this practice is now before me in the third number of the new 

 edition of Layard's "Birds of South Africa," which, although 

 only issued to the subscribers within these last few days, is dated 

 on the cover "May, 1875 !" As two new genera {A'cthocichla 

 and Neocichla) are instituted herein, the result is to give these 

 names an unjust priority of fifteen months over what they are 

 legally entitled to. This seems to be a still easier method of gaining 

 precedence than the American practice of publishing telegraphic 

 bulletins of new discoveries, and will not, I trust, be persevered 

 in, if attention is called to it. F;Z.S. 



August 7 



Protective Mimicry 



I HAVE been reading over in the file of Nature the contro- 

 versy that arose out of Mr. Alfred Bennett's paper at the British 

 Association in 1870, on "Natural Selection from a Mathematical 

 Point of View," in which he attacked Darwin's theory on what 

 seems to be one of its strongest points, namely, protective 

 mimicry. I do not feel certain whether he is right or not in 

 denying that natural selection is adequate to produce mimicry. 

 The argument really depends on a question of fact, namely, 

 whether the first variation could be great enough to be useful to 

 its possessor ; and from the great comparative variability of 

 colour, I see no decided impossibility in this. 



But the writers m that controversy neglected other facts of 

 colour which it seems impossible for natural selection to pro- 

 duce, from the infinite improbability of a first variation ever 

 occurring. One of these is the change of colour with the 

 seasons in such animals as the ermine, which is brown in 

 summer and white in winter. Had the ermine been either 

 permanently brown or permanently white, there would have been 

 nothing wonderful in it, but it seems impossible that the cha- 

 racter of becoming white in the winter and brown in the summer 

 could ever have originated in ordinary spontaneous variation, 

 without a guiding intelhgence. 



Another case of at least equal difficulty is the case of change 

 of colour for the purpose of protection, from moment to moment. 

 The chameleon is the best known instance of this, but I believe 

 there are many such cases among fishes. It seems utterly im- 

 possible for such a character to originate in spontaneous un- 

 guided variation. Joseph John Murphy 



Old Forge, Dunmurry, Co. Antrim, July 20 



A REMARKABLE instance of this phenomenon is shown in a 

 small crustacean, of the genus " Rypton" (Mr. Spence Bate has 

 not yet determined whether it be a new species or no). This 

 very delicate little animal is found only in holes in the coral 

 inhabited by the common "Echinus" of Mauritius; its colour 

 is a deep purple, with four longitudinal stripes of a much lighter 

 tint ; and this is precisely the pattern of the spiiies of the said 

 Echinus. WiLMOT H. T. Power 



\ Ophiuchi 



I AM going to undertake the calculation of elements of X 

 Ophiuchi, which you proposed to calculators in Nature, vol. 

 xiv. p. 29. I shall also within a short time give orbits of 7 Coronge, 

 which has not been separated as far as I know since spring, 

 1867, when it was obseived in Harvard College, and of 

 I Libree (Scorpii). About the latter binary star we know but 

 very little. Madler has given a circular orbit with a period 

 of over 100 years, while Thiele gives a highly eccentric orbit 

 with a period of about fifty years. It may very likely be found 

 that the older determination is the most trustworthy, but the 

 case deserves a thorough examination, which I am going to 

 make. I have been engaged in a re-determination of elements 

 of 6 Coronse, by which the long period has been re-ascertained. 



There are different other double stars which with advantage 

 might be inquired into, and thus prevent different investigators 

 from confining themselves to the same objects, while others 

 remain uncared for. I hope that you will be kind enough to 

 publish the above remarks in your widely circulated paper. 



Markree Observatory, CoUooney, William Doberck 



Ireland, July 17 



The Cuckoo 



The cuckoo is still singing in this part of the country. I 

 may mention, as a point of some interest, that the note of this 

 bird in South Germany is precisely the same in pitch as it is 

 here, the observations in both cases having been made with a 

 tuning-fork in the month of May. 



Can any of your readers inform me whether the cuckoo in all 

 parts of the country is in the habit of occasionally singing the 

 cue without the koo ? George J. Romanes 



Ross-shire, July 24 



THE FERMENTATION OF URINE AND THE 

 GERM THEORY 



CAN Bacteria or their germs live in liquor potassze 

 (Pharm. Brit.) when it is raised to the boiling-point 

 (212° F.) ? Such is now the simple issue to which cer- 

 tain great controversies have been reduced. If Bacteria 

 germs cannot resist such an exposure, then, by M. 

 Pasteur's own impHcit admission, his exclusive germ- 

 theory of fermentation must be considered to be over- 

 thrown by the broader physico-chemical theory. The 

 truth or not of M. Pasteur's germ-theory is the central 

 question in dispute, but standing on either side, or in 

 close juxtaposition, are two dependent subjects of contro- 

 versy whose importance for biological science and for 

 medicine is even greater. 



The question whether living matter can or cannot 

 originate de novo, for example, depends upon the answer 

 which is to be given to the question whether Bacteria 

 and their germs are or are not killed in boiling liquor 

 potassae. This, also, is practically admitted by M. 

 Pasteur in his comments {Comptes Rendus, July 1 7) upon 

 my recent experimental evidence. 



The other subordinate problem, the solution of which 



