independently of the general colouring, and he [Mr. Merrifield] obtained from the same brood individuals showing summer markings with summer colouring, summer markings with an approach towards spring colouring, spring markings with summer colouring, and spring markings with almost the spring colouring.' 34 As a rule, a cooler temperature gave darker colours, and cooling of the larvæ without a subsequent forcing of them in a warm temperature gave the darkest moths. In the common butterfly, Vanessa urtica, a moderately low temperature generally deepened the colouring to some extent, lowered the tone of the yellow patches, and spread the dark portions. It appeared moreover that the size and, though less markedly, the shape of the wings were affected by the temperature of breeding; or, the wings being somewhat reduced in size, the scales became scanty and deficient in pigment so as to show the membrane of the wing.35 It is also interesting to note that while some cooled specimens of Vanessa urtica bore resemblance to a northern variety, some of the heated specimens were like a southern form, and that (as was indicated by C. W. Barker) the rain-period butterflies of Natal differ from those of the dry period precisely in all those directions in which variation was obtained by cooling. Again we have in these experiments a peep, so to say, into Nature's ways of originating new species. Finally we have the well-known experiments of E. B. Poulton, who changed the colours of several common species of British caterpillars from green to various hues of brown and grey by rearing them amidst darkened surroundings (black and brown twigs were mixed with their food, or they were placed in dark-painted boxes, and so on), and the experiments of J. T. Cunningham on fishes. Poulton's experiments are so well known to the general reader from his most interesting popular book Colour in Animals, as also from Wallace's Darwinism, that a mere reference to these now classical researches is sufficient.36 As to the experiments of J. T. Cunning * The original accounts of Mr. Merrifield were published in the Transactions of the Entomological Society of London. F. A. Dixey has summed them up in Nature, December 23, 1897 (vol. lvii. p. 184), reproducing some of the very interesting drawings. A detailed account of Weismann's experiments (frequently mentioned in his previous writings) was only published in 1895, in Zoologische Jahrbücher, Abtheilung für Systematik, Bd. viii. 35 F. A. Dixey expressed, in connection with Merrifield's experiments, the idea that certain of the modifications produced in Vanessa atalanta by both heat and cold show a return towards the ancestral type of V. callirhoë and to a still older form of Vanessa. Fischer, on the basis of his extensive experiments, expressed also the idea that the variations provoked in butterflies by different temperatures are arrests of development (Hemmungs-Erscheinungen), in consequence of which older atavistic forms are fixed; and he developed the same ideas in a book, Neue experimentelle Untersuchungen und Betrachtungen über das Wesen und die Ursachen der Aberration in der Faltergruppe Vanessa, Berlin, 1896. The idea is, however, contradicted by Urech, and needs confirmation. ** The experiments are most suggestive, and raise a number of secondary questions, for which the original memoir must be consulted in Transactions of the ham, although they are less known, they are also very conclusive. It is known that in most fishes the upper surface is more or less coloured, while the lower surface remains uncoloured and has a silvery aspect; and that this double coloration is generally supposed to have originated as a means of protection for the fishes. It evidently permits a fish not to be detected by its enemies. However, Cunningham made experiments in order to see whether the absence of coloration on the ventral surface may not be due to the absence of light falling upon it. He consequently kept a number of young flounders in two separate basins, one of which was provided with mirrors so as to illuminate the lower surface of the fishes as well, while the other was of the ordinary sort. The result was that after a time a certain amount of coloration appeared on the ventral sides of the flounders of the first basin, first in the middle portion of the body, and then spreading both ways towards head and tail. It is true that small spots of pigment appeared on the ventral surfaces of a few fishes of the second basin as well, as they often do in nature; but the percentage of spotted individuals was small and the spots did not increase.37 It must be confessed that all these researches are only first steps towards the foundation of a science of which the need is badly felt— the physiological experimental morphology of animals. These first steps are in the right direction; but they are very slow, and prohably will remain slow so long as the matter is not taken in hand by physiologists. Consequently, without even attempting to touch upon the wide subject of variation in free nature, or of palæontological evidence, I will permit myself to mention here one set only of observations taken from this vast domain, because they throw some additional light upon the facts mentioned in the foregoing pages. I mean the well-known wonderful collection of land molluscs which was brought together by J. T. Gulick, and which illustrates the incredible amount of variation that takes place in the family of Achatinellæ on the small territory of the Oahu Island of the Sandwich group. Having lately had the privilege of examining this collection at Boston under the guidance of Professor Hyatt, who gave me full explanations about the work he is doing now upon this collection, I will take the liberty of adding a few words to what has been said about it by Wallace and Romanes. The Oahu Island has, as is known, a range of mountains nearly forty miles long along Entomological Society of London, 1892, p. 293 (good Summary by G. H. Carpenter in Natural Science, April, 1893, ii. 287), as also the memoir of Miss Lilian Gould and two of W. Bateson in the same volume. The memoir of E. B Poulton contains also observations subsequent to the publication of his book. 87 Journal of the Marine Biological Association, 1893, iii. p. 111. Summed up in many reviews; also in Miss Newbigin's book. Considerations of pace compel me to leave for another occasion the 'wilful' changes of colour in certain animals which may be better dealt with in connection with mimicry. its eastern coast. Several valleys are excavated on the inner slope of this range, and each valley has its own representatives of the Achatinellæ land molluscs, which could be described in full conscience as separate species, more than 100 in number, with several hundred varieties. A broad valley separates this range from another shorter and lower range running along the opposite coast. The doubts which the author of Darwinism has expressed concerning the complete identity of climatic conditions in all the valleys are probably justified. There is, I was told, a slight difference between the maritime and the land slope of the first range, and there is, so far as information goes, a difference in the rainfall at one end of this range and at its other end. But when one sees the strikingly minute and yet persistent differences between the species and varieties-each limited to its own valley or valleys-and grows acquainted with Professor Hyatt's many years' work in order to follow the molluscs in their migrations from the maritime slope to the different valleys of the land slope, and next across the flat land towards the second ridge, and sees the growth of this or that minute distinction in the course of time and migration, one cannot but accept the explanation of Professor Hyatt. Variation once having set in a certain direction has continued in that direction so long as conditions not unfavourable for it have prevailed; and isolation, geographical and physiological, has prevented cross-breeding. On the other side, on examining the collection of Gulick, one feels that one must overstrain the potentialities of that admirable theory of natural selection if one attempts to explain through it the maintenance and the growth of such insignificant yet persistent specific characters, as, for instance, the very slightly different markings appearing in this or that species, and gradually developed in the next ones. We have thus a solid body of evidence growing from year to year, and showing us how variations in the structure and the forms of animals and especially of plants are arising in nature as a direct result of the mutual intercourse between organism and environment. To this Weismann and his neo-Darwinist' followers will probably reply that all these facts are of little value, because acquired characters are not transmitted by heredity. We have seen that in plants they are. No botanist evidently believes that a scar in a plant or a mutilation can be transmitted, any more than a scar in the ear of a man or a clipped tail in a rat, which, as Celesia remarks, is made to breed immediately after the tail has been clipped. But the most prominent botanists are of opinion that if the equilibrium between nutrition (in its wide sense) and expenditure has been broken, and a new adjustment has been produced in the plant, this adaptation will be transmitted in most cases by heredity; and that so long as the new conditions last, the plant will not have to begin its adjustment afresh in each generation. The effect will be cumulative. We are consequently authorised to suspect-although proof or disproof of this has not yet been attempted-that something similar will be found in animals; that, for instance, the cave animals of Viré, born from his Asellus specimens in the underground laboratory, will not have the eyes so developed, and their olfactory organs so undeveloped, as they are in an Asellus taken from an openair stream. As to Weismann's theoretical views one remark only need be added here to what has been already said in a previous Review (April 1894), namely, that most of the founders of our present knowledge about fertilisation refuse to accept Weismann's theories, and that one of them, Boveri, has lately proved by continuing his series of remarkable discoveries that the whole question of heredity is still in a state in which generalisations like Weismann's are premature. They surely stimulate research. But no sooner are they born than they must be recast, new discoveries still rapidly following each other. But this subject is so interesting in itself that it will have to be dealt with separately on some future occasion. P. KROPOTKIN. INTERNATIONAL BOAT-RACING SINCE the date of last Henley Regatta correspondence and controversy have arisen in the Times and other journals on the subject of a suggestion that in future Henley Regatta should be closed against foreign entries. Three distinct classes of views seem to have been promulgated. These are (1) to close it unconditionally; (2) to do so subject to the understanding that some alternative time and place should be arranged whereat amateur visitors shall, if desirous, be able to try conclusions with the best English opponents; (3) to let the regatta remain under its present regulations. In order to appreciate the situation and the full bearing of the several proposals, it seems desirable, as a prelude, to examine the history and records of prior aquatic international rencontres. EARLIEST MATCHES Professionals from over-sea were the first to measure their strength against British oarsmen. In 1863 Green, the Australian, met Robert Chambers, of the Tyne, over the Thames champion course. In 1866 Hammill, of Pennsylvania, tried conclusions with Harry Kelley on the Tyne. In each case the Britisher showed decisive superiority. In 1876 Joseph Sadler, then elderly and grizzled, lost the Thames championship to Trickett, the Australian. Since that date British professional oarsmanship has been but second class compared to Australian and Canadian talent, and even against the best scullers of the States. These three professional sculling contests were international in every sense; British aquatic supremacy had been challenged in each case, and on each occasion the British champion of the day did battle. In 1869 amateur international boat-racing was first seen in this country. Harvard, U.S., challenged Oxford, who were winners of the University match that year. In 1872 the Atalanta Club of New York challenged the London Rowing Club, who held the Stewards' Cup of Henley. Both these races were for four oars, were rowed over the Putney course, and were won by England. In 1876 the |