Sept. I, 1881] 



NATURE 



403 



rely on tlie assistance of friends in every department of 

 ! cience. 



Certainly, however, this is an opportunity on which it may be 

 well for us to consider what have been the principal scientific 

 results of the last half-century, dwelling especially on those with 

 which this Association is more directly concerned, either as being 

 the work of our own members, or as having been made known 

 at our meetings. It is of course impossible within the limits of 

 a single address to do more than allude to a few of thee, and 

 that very l)riefiy. In dealing with so large a subject I first hoped 

 that I might take our annual volumes as a text-book. This, 

 however, I at once found to be quite impossible. For instance, 

 the first volume commences with a Report on Astronomy by 

 Sir G. Airy ; I may be pardoned, I trust, for expressing my 

 pleasure at finding that tbe second was one by my father, on the 

 Tides, prepared like the preceding at the request of the Council ; 

 then c imes one on Meteorology by Forbes, Radiant Heat by 

 Baden Powell, Optics by Brewster, Mineralogy by Whewell, and 

 so on. My best course will therefore be to t'.ke our different 

 Sections one by one, and endeavour to bring before you a 

 few of the principal results which have been obtained iu each 

 department. 



The Biological Section is that with which I have been most 

 intimately associated, and with which it i*, perhaps, natural that 

 I should begin. 



Fifty years ago it w as the general opinion that animals and 

 plants came into existence just as we now see them. We took 

 pleasure in their beauty ; their ad.iptation to their habits and 

 mode of life in many cases could not be overlooked or misunder- 

 stood. Nevertheless, the book of Nature was like some richly 

 illuminated missal, written in an unknown tongue; the graceful 

 forms of the letters, the beauty of the colouring, excited our 

 wonder and admiration ; but of the true meaning little was 

 known to us ; indeed w e scarcely realised that there was any 

 meaning to decipher. Now glimpses of the truth are gradually 

 revealing themselves ; we perceive that there is a reason — and 

 in many cases we know what that reason is — for every difference 

 in form, in size, and in colour ; for every bone and every featlier, 

 almost for every Iiair. Moreover, each problem which is solved 

 opens out vi-tas, as it were, of others perhaps even more interest- 

 ing. With this great change the name of our illustrious ccuntr)-- 

 man, Darwin, is intimately associated, .and the year 1859 will 

 always be memorable in science as having produced his great 

 work on "The Origin of Species.' In the previous year he 

 and Wallace had published short papers, in which they clearly 

 state the theory of natural selection, at which they had simul- 

 taneously aiul independently arrived. We cannot wonder that 

 Darwin's vi<:ws should have at first excited great opposition. 

 Nevertheless from the first they met with powerful support, 

 especially, in this country, from Hooker, Huxley, and Herbert 

 Spencer. The theory is based on four axioms : — 



" I. That no two animals or plants in nature are identical in 

 all respects. 



"2. That the offspring tend to inherit the peculiarities of 

 their parents. 



"3. That of those which come into existence, 01. ly a small 

 number reach maturity. 



" 4. That those, which are, on the whole, best adapted to the 

 circumstances in which they are placed, are most likely to leave 

 descendants." 



Darwin commenced his work by discussing the causes and 

 extent of variability in animals, and the origin of domestic 

 varieties ; he showed the impo.-sibility of distinguishing between 

 varieties and species, and pointed out the wide differences 

 which man has produced in some cases — as, for instance, in our 

 domestic pigeons, all unquestionably descended from a common 

 stock. He dwelt on the stj'uggle for existence (which has since 

 become a household word), aud which, inevitably resulting in 

 the survival of the fittest, tends gradually to adapt a;ny race of 

 animals to the conditions in which it occurs. 



While thus, however, showing the great importance of natural 

 selection, he attriliuted to it no exclusive influence, but fully 

 admitted that other causes — the use and disuse of organs, sexual 

 selection, &c. — had to be taken mto consideration. Passing on 

 to the difficulties of his theory he acciunted for the absence of 

 intermediate varieties between species, to a great extent, by the 

 imperfection of the geological record. 



But if the geological record be imperfect, it is still very 

 instructive. The further palteontology has progressed the more 

 it has tended to fill up the gaps between existing groups and 



species, while the careful study of living forms has brought into 

 prominence the variations dependent on food, climate, habitat, 

 and other conditions, and shown that many species long sup- 

 posed to be ab. olutely distinr-t are so closely linked together by 

 intermediate forms that it is difficult to draw a satisfactory line 

 between them. 



The principles of classification point also in the same direction, 

 and are based more and more on the theory of descent. Biolo- 

 gists endeav. ur to arrange animals on what is called the " natural 

 system." No one now places whales among fi>h, bats among 

 birds, or shrews with mice, notwithstanding their externjil 

 similarity ; and Darn in maintained that "coimiunity of de-cent 

 was the hidden bond which naturalists had been unconsci'iusly 

 seeking." How else, indeed, can we explain the fact that the 

 framew ork of bones is so similar in the arm of a man, the wing 

 of a bat, the fore-leg of a horse, and the fin of a porpoise — 

 that the neck of a giraffe and that of an elephant contain the 

 same number of vertebra; ? 



.Strong evidence is, moreover, afforded by embr; ology ; by the 

 presence of i-u.iimentary organs and transient characters, as, for 

 instance, the existence in the calf of certain teeth which never 

 cut the gums, the shrivelled and useless wings of some be ties, 

 the presence of a series of arttries in the embryos of the higher 

 Vertebrata exactly similar to those which supply the gills in 

 fishes, even the spots on the young blackbird, the stripes on the 

 lion's cub; these, and innumerable oiher facts of the same 

 character, appear to be incompatible with the idea that each 

 species was specially and independently created ; and to prove, 

 on the C'iUtrary, that the embryonic stages of species show us 

 more or less clearly the structure of their ancestors. 



Darwin's view s, however, are still much misundei-stood. I 

 believe there aie thousands who consider that according to his 

 theory a sheep might turn into a cow, or a zebra into a horse. 

 No one would more confidently withstand any such hypothesis, 

 his view being, of course, not that the one could be changed 

 into the other, but that both are descended from a common 

 ancestor. 



No one, at any rate, will question the immense impulse which 

 Darwin has given to the study of natural history, the number of 

 new views he has opened up, and the additional interest which 

 he has aroused in, and contributed to, Biologfv. When we were 

 young wc knew that the leopard had spots, the tiger was striped, 

 and the lion tawny ; but why this was so it did not occur to us 

 to ask ; and if we had asked no one would haveanswered. Now 

 we .-ee at a glance that the stripes of the tiger have reference to 

 its life among jungle-grasses; the lion is sandy, like the desert ; 

 while the markings of the leopard resemble spots of sunshine 

 glancing through the leaves. 



The science of embryology may almost be said to have been 

 created in the last half-century. Fifty years ago it was a very 

 general opinion that animals which are unlike when mature, were 

 dissimilar from the beginning. It is to Von Baer, the discoverer 

 of the mammalian ovum, tliat we owe the great generalisation 

 that the development of the ega; is in the main a progress from 

 the general to the special, in fact, that embryology is the key to 

 the laws of animal development. 



Thus the young of existing species resemble in many cases the 

 mature forn s which flourished in ancient times. Huxley has 

 traced up the genealogy of the horse to the Miocene Anchi- 

 therium. In the same way Gaudry has called attention to the 

 fact that just as the individual stag gradually acquires more and 

 more complex antlers : having at first only a single prong, in tbe 

 next ye;ir two points, in the following three, and so en ; so the 

 genus, as a whole, in Middle Miocene times, had two pronged 

 horns ; in the Upper Miocene, three ; and that it is not till the 

 Upper Pliocene that we find any species with the magnificent 

 antlers of our modem deer. It seems to be now generally 

 admitted that birds have come down to us through the Dino- 

 saurians, and, as Huxley has shown, the profc und break once 

 supposed to exist between birds and reptiles has been bridged 

 ever by the discovery of reptilian birds and bird-like reptiles ; so 

 that, in fact, birds are modified reptiles. Again, the remarkable 

 genus Peripatus, so well studied by Moseley, tends to connect 

 the annulose and articulate types. 



Again, the structural resemblances between Amjihioxus and 

 the .\scidi.ans had been pointed out by Good ir ; and Kowalev^ky 

 in 1S66 showed that these were not mere analogies, but indicated 

 a real affinity. These observations, in the words of Allen 

 Thomson, " hav^- produced a change little short of revolutionary 

 in embryological and zoological views, leading as they do to 



