April 29, 1909] 



A' A TURE 



247 



LETTERS TO THE EDITOR. 

 [TIic Edilot does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can lie undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications.] 



Australian Kinship. 



In a note which appeared in Nature of April i d propos 

 of my paper on terms for human relationsiiips (British 

 Academy), the writer suggested that our l^nowledge of 

 Australian society was still very incomplete. Even as to 

 Arunta rules and customs, he said, our informants differed 

 grratly in their reports. There is now reason to suppose, 

 however, that our informants, Messrs. Spencer and Gillen, 

 and, later, the Rev. Mr. Strehlow, are not really at odds. 

 The impression that they disagreed was caused by some 

 letters of Mr. Strehlow in Globus and elsewhere; but now 

 that he has published two parts of his " Die Arunta und 

 I.oritja-Stamme " (Frantcfurt : Baer and Co., 1907, 1908), 

 it becomes clear that he has merely studied branches of 

 the .Arunta " nation " not within the range of the work 

 of Messrs. Spencer and Gillen, and that his natives differ, 

 not only in customs and beliefs, but more or less in 

 language, from those of the English explorers. 



The differences are matters of detail ; the broad outlines 

 of custom and myth are identical. I ventured to e.xpress 

 this opinion in Man, and was confirmed in my view by 

 finding that it is held by Mr. N. W. Thomas (" Folk- 

 Lore," March 30, 1909). He writes that Mr. Strehlow 's 

 second volume " confirms the belief that local differences 

 of considerable magnitude exist, not only in belief, but 

 also in social organisation." 



In all probability both Messrs. Spencer and Gillen and 

 Mr. Strehlow are right as regards the natives whom they 

 have studied. Mr. Strehlow 's full knowledge of the 

 languages or dialects makes his book " masterly," as Mr. 

 'I'homas says, but the book does not invalidate the results 

 of the English inquirers. An English translation would 

 save trouble to readers in this country who are not too 

 familiar with German. A. Lang. 



Forms, Markings, and Attitudes in Animal and Plant 

 Life. 



The object of this letter is to suggest what I may call 

 a collateral theory of mimicry, and not in any sense a 

 complete theory. It is based upon facts or groups of 

 facts, many of which are very well known, but all of 

 wliirh have passed under my own observation. 



Notwithstanding the great variety of form in leaves, 

 there is general agreement as to the primary character 

 of a simple ovate leaf, and the bi-facial form of the leaf 

 is in obvious correlation with the great functions of trans- 

 piration and assimilation. The bi-facial leaf-like form of 

 the leaf-insect (Phyllium) is not in correlation with any 

 such essential metabolic functions, but it is correlated with 

 the mode of life of the insect. The expression " mode of 

 life " is sufficiently vague ; it represents the combination 

 of physiological reactions which make up the outward 

 life of the animal. What these reactions are cannot 

 always be stated in precise language, and until they can 

 be so stated our knowledge has not advanced very much 

 in regard to a particular case. 



The cryptozoic habit of so many animals is the ex- 

 pression of reactions which may be conveniently classified 

 together under the term cryptotaxis. Thus the conceal- 

 ment afforded by protective resemblance is one example 

 of this general tendency; living under logs, or bark, or 

 below the surface of the ground is another. Prof. Loeb, 

 as I understand him, has attempted to throw discredit on 

 this tendency in so far as he reduces it to a manifestation 

 of stereotropism ("The Dynamics of Living Matter," 

 1906, p. 157) ; but stereotropism may, and obviously does, 

 •coexist with cryptotaxis, as may be verified any day in 

 the behaviour of snakes, land-leeches, and land-planarians. 



The leaf-butterfly (Kallima) also admirably lives up to 

 its name, but in a different sense; for, whereas Phyllium 

 has a dorsoventrally flattened body, Kallima has a normal 

 body, and resembles a leaf only when at rest with closed 

 wings. The puna of anothr-r butterfly, Troides darsius, 



NO. 2061, VOL. 80] 



resembles a crumpled yellow leaf ; but it is not only 

 amongst insects that we find leaf resemblances. It occurs 

 also amongst fishes. Besides the extraordinary case of 

 Phyllopteryx, the young sea-bat (^Plata.v vespertilio) 

 resembles a simple yellow leaf, the dorsal, ventral, and 

 anal fins assisting to form the contour line, while the 

 caudal fin is glass-clear (Spolia Zeylanica, ii., 1905, p. 51). 

 Drifting yellow leaves which have fallen from mangroves 

 and other maritime trees are common enough in the sea 

 and backwaters. 



Animals which resemble the same thing resemble one 

 another ; but whereas the resemblance of a leaf-fish 

 (Platax) to a leaf is a real resemblance, advantageous to 

 the fish, its resemblance to a leaf-butterfly is accidental, 

 and of no value to either. The important fact is their 

 common possession of a fundamental form, namely, that 

 of a leaf. 



Of other forms which are widely distributed amongst 

 different families, orders, and even classes, I may mention 

 the ant-form and the tadpole-form, without going into 

 further particulars. 



With equal brevity allusion may be made to familiar 

 markings, widely distributed without reference to mutual 

 resemblances, but conforming to common physiological 

 reactions. Such, for example, are longitudinal stripes or 

 bands, transverse bars or rings, bright spots on a dark 

 ground, dark spots on a pale ground, &c. In all such 

 cases I suggest that the primary fact is the conformity to 

 a fundamental pattern, which is itself the expression of 

 a pigment-reaction, the causes of which have not yet been 

 reduced to a definition. Any advantage which this con- 

 formity to a common standard may confer is a secondary 

 factor which may conduce to the preservation of the 

 species by natural selection. 



Lastly, with regard to attitudes there is much to be 

 said, but I must be brief. One of the most telling 

 examples of general conformity of attitude is the bi-pedal 

 posture of all birds, some reptiles, and many mammals. 



The little palm-squirrels (Funambulusl and tree-lizards 

 (Calotes) are often seen associated together on the same 

 tree, and it is therefore the more noticeable that they 

 have in common a singular habit of remaining in one 

 spot with the fore-body somewhat raised, and then jerk- 

 ing the fore-body up and down several times in rapid 

 succession wdiilst clinging to the trunk or branch of a 

 tree. I do not know what the precise significance of this 

 bobbing movement may be, but they both practise it. 



The only other attitude which I desire to mention is 

 the vertical attitude assumed by some fishes. Some years 

 ago I described and published an ideal picture of the 

 vertical swimming attitude of Amphisile strigata (Zoo- 

 logical Results, part vi., 1902, p. 719). More recently 

 the late Mr. W. Saville Kent told me that he had seen 

 the same thing, and had kept the fish in an aquarium, 

 whereas I had only seen it from a boat, swimming in a 

 small shoal in the sea. I was glad of the confirmation 

 of the vertical attitude; but upon 'showing my figure to 

 Mr. Saville Kent, he pointed out to me that the head 

 is not directed upwards, as there represented, but down- 

 wards, as if to feed from the bottom. What I saw were 

 swimming in mid-water, and as the body has a pro- 

 nounced amphioxine form, it was impossible to be certain 

 which end was uppermost. This uncommon vertical atti- 

 tude, with head directed downwards, is not without parallel 

 amongst fishes, having been observed by Dr. Abbott in 

 the rase of the " mud sunfish " {Acantharchiis homotis) 

 in 1884. Arthur Willey. 



Colombo, Ceylon, April 4. 



The Simple Equivalent of an Alternating Circuit of 



Parallel Wires. 

 Is N.ATURE of January 30, 190S, some results were 

 quoted by me with reference to the effective inductance of 

 two long parallel wires when the change of current dis- 

 tribution due to frequency is taken into account. These 

 were extended later {Phil. Mag., February, 1909) to meet 

 the case in which the wires are very close together. Pend- 

 ing more detailed publication, the following developments 

 and extensions may be of Interest from the practical point 

 of view, as they do not require the construction of special 



