August 29, 1907J 



NATURE 



457 



ocular organ shines with an ultramarine light, whilst the 

 middle of the five ventral organs is sky-blue and the anal 

 organs are ruby-red. It may also be observed that even in 

 preserved specimens, when examined in a strong light, the 

 different organs seem to shine with different colours, 

 although there is under such conditions no actual emission 

 of light. Furthermore, in some forms (e.g., Calliteuthis) 

 there are chromatophores in the superficial layers of the 

 integument over the luminous organs, through which the 

 light admitted must pass. A somewhat similar arrange- 

 ment obtains in the curious structures in Chirotetithis, which 

 were regarded by Joubin at the time of their discovery 

 as " thermoscopic eyes," but which are, I think 

 rightly, in the present state of our knowledge, con- 

 sidered to be a special kind of luminous organ. 

 In these instances the function of the superficial 

 chromatophores may be to colour the light which passes 

 through them. 



The question of the utility of these variously coloured 

 lights to the creature possessing them admits of an answer 

 which is, at all events, extremely plausible. It was sug- 

 gested in the case of deep-sea fishes by Brauer, and has 

 been adopted by Chun in reference to the Cephalopoda. 

 They serve as recognition marks by which the various 

 species can identify their fellows ; just as certain colour 

 patches in the plumage of birds enable them to find their 

 mates, so in the darkness of the ocean abysses do these 

 fairy lamps serve their possessors. Another and perhaps 

 even more obvious utility is suggested by the general dis- 

 tribution of these organs. It has above been pointed out 

 that they are, almost without exception, on the ventral 

 aspect of the body, that is, the inferior surface in the posi- 

 tion in which the animal habitually swims. It must 

 happen, therefore, that when the creature is moving over 

 the floor of the ocean in the quest for food, this must be 

 illuminated by its lamps, and the advantage of a series of 

 searchlights playing over the ground will be at once 

 apparent. 



Finally we have the question : How is the light pro- 

 duced? To this we can only say that this is an instance of 

 the transformation of one kind of energy into another. 

 We are quite familiar with the production of heat in the 

 animal body by the processes of oxidation which go on in it ; 

 we are also familiar with the production of kinetic energv 

 when a muscle contracts under a nervous stimulus ; and 

 we are also aware that electric discharges are produced 

 under similar conditions in certain organs of the Torpedo 

 and other fish. The production of light is a phenomenon of 

 the same kind. When we can explain how stimulation 

 applied to a nerve causes contraction in a muscle, then, 

 and not till then (so far as I can see), shall we be within 

 reasonable distance of explaining the action of these living 

 lamps. 



One point is worthy of notice which has been ascertained, 

 not by experiments on the Cephalopoda, but on other 

 animals, namely, the remarkable economy of this illu- 

 minant. A perfectly infinitesimal proportion of the energy 

 expended is wasted on the production of heat. From 

 this point of view animal phosphorescence puts to 

 shame our most modern devices. Whether we shall 

 ever be able to rival Nature in this respect remains to 

 be seen. 



We have thus shown how rapid has been the growth of 

 our knowledge regarding the distribution and structure of 

 these fascinating organs, and yet how little we have learned 

 of the mode of their operation, and we end, as all scientific 

 inquiries end when pursued far enough, with a confession 

 of ignorance. 



What I have ventured to lay before you are a few of 

 the fruits of the little garden plot in whose culture I have 

 been privileged to take a humble share. If it has appeared 

 to you tliat the labour spent upon their production by a few 

 enthusiastic workers has been well expended ; if they show 

 that in this, as in any other group of animals, the study 

 of small details conscientiously carried out leads to pro- 

 blems of the deepest interest, my object in the preparation 

 of this .\ddress will have been fullv achieved. 



NO. 1974, VOL. 76] 



MATHEM.iTICS .4.VD PHYSICS AT THE 

 BRITISH ASSOCIATION. 

 r\^ Thursday, August i, at lo a.m.. Prof. A. E. H. 

 ^^ Love, F.R.S., read his presidential address, which 

 has already appeared in full in these columns (see Nature. 

 August i). A vote of thanks, moved by Sir D. Gill and 

 seconded by Sir G. Darwin, was carried with acclamation. 



The Hon. R. J. Strutt commenced the ordinary proceed- 

 ings with a paper on helium and radio-activity in common 

 ores and minerals. He was inclined to attribute the 

 helium which can be obtained from minerals, not to a 

 radio-activity of the rocks themselves, but to the radium 

 which they contain. The evidence on which this con- 

 clusion was based is that the ratio of radium to helium 

 present is nearly constant. A great exception occurs in 

 the case of beryl, which shows no radio-activity, but con- 

 tains a large' quantity of helium. Prof. Rutherford 

 suggested that thorium should be looked for in beryl as 

 a source of the discrepancy. In his reply, Mr. Strutt 

 stated that he had found thorium in granite but not in 

 beryl in sufficient quantities to afford an explanation of 

 its peculiar behaviour. 



Lord Kelvin followed with a paper on the motions of 

 ether produced by collisions of atoms or moleciiles con- 

 taining or not containing electrions. To him it seems 

 extremely improbable that differences of grouping atoms 

 all equal and similar should suffice to explain all the 

 different chemical and other properties of the great number 

 of substances now commonly called chemical elements. 

 The impossibility of the transmutation of one element into 

 any other he declared to be almost absolutely certain. 

 The ether he takes as an elastic, compressible, non- 

 gravitational solid. It is, however, only under the 

 enormous forces of attraction or repulsion exertetl by atoms 

 on ether that augmentation or diminution of its density 

 is practically influential. Purely dynamical reasoning 

 leads him to infer generally similar theorems for an atom 

 to those worked out by Heaviside for an electron. The 

 association of atoms with electrions (or atoms of resinous 

 electricity), and the interaction of both with the ether, 

 form the' basis of a general explanation of physical 

 phenomena. 



In a paper on secular stability. Prof. Lamb explained 

 the difference between ordinary or temporary stability, 

 i.e. stability as asserted by the method of small oscilla- 

 tions, and secular stability, i.e. stability when account is 

 held of possible frictional forces ; and he gave an experi- 

 mental illustration of the latter kind. A pendulum hangs 

 by a Hooke's joint from the lower end of a vertical shaft 

 which can be made to rotate by a pulley with constant 

 angular velocity u: The effect of the rotation is that its 

 two circular component vibrations have different periods, 

 that one being the faster the direction of revolution of 

 which agrees with that of the shaft. The criterion _ of 

 secular stability imposes a limit to the speed for which 

 the vertical position of the shaft is stable ; for_ speeds 

 higher than the limiting one a new position of equilibrium 

 is possible in which the pendulum rotates at a constant 

 inclination 9 given by cos fl = M,f;I/(A-C)a.^ where A and 

 C are the two principal moments of inertia of the 

 pendulum at the joint. 



The beginning of the session on Friday had been allotted 

 to a discussion on the constitution of the atom, and the 

 committee of the section had not been in error in expect- 

 ing that this would be of intense interest. Prof. Ruther- 

 ford, whom we now have permanently in this country, 

 opened it with a speech which was specially intended to 

 suggest lines for discussion rather than to be a dogmatic 

 statement of his own views. It was perfectly clear, how- 

 ever, that he regarded the electron as having come to 

 stay,' although at present it is impossible to decide whether 

 the' electrons which are set free in radio-activity or are 

 revealed bv the optical properties of an atom are merely 

 an outer circle or are a revelation of the internal consti- 

 tution of the inner core of the atom. He declared in 

 favour of a kinetic view of the atom in opposition to 

 statical views such as that developed by Lord Kelvin. 

 Only on a kinetic theory could the great velocity of the 

 particles be explained.' Sir O. Lodge in his contribu- 



