414 



NATURE 



\Sept. 9, 1875 



elements of which it is composed ; and principally by the recog- 

 nition of the secondary nature of cell- walls, the close connection 

 or even continuity of the nerves with other textures, and the 

 identity of the white corpuscles of the blood with amoeboid or 

 undifferentiated corpuscles outside the vessels. The origin of 

 every living corpuscle from corpuscles pre-existing is no longer 

 difficult to imagine, but may, I incline to think, be almost 

 looked on as proved. The history of each may be traced back 

 through conjugated germs to the corpuscles of preceding genera- 

 tions in uninterrupted succession, and the pedigree of the 

 structural elements is seen to differ in no way from that of 

 individual plants or animals. It is true, indeed, that no abso- 

 lute proof exists that new living corpuscles originating by mere 

 deposit are not added to the others ; l)ut the evidence against such 

 a thing taking place is exactly of the same description as that 

 which exists against spontaneous generation of independent 

 organisms, namely, that things previously unexplained by the 

 theory of parentage are explained now, while, on the other 

 hand, there is no sufficient evidence of the origin of life by any 

 other mode. 



Leaving histology (he said), I shall devote the rest of my re- 

 marks to the morphology ot the Vertebrata. Here I am less 

 disposed to indulge a gratulatory vein. No doubt within the 

 last dozen years we have had work to be grateful for. Worthy 

 of a prominent place in this, as in other departments of anatomy, 

 is the encyclopaedic work, the " Le9ons," of Milne-Edwards, 

 invaluable as a treasury of reference to all future observers ; 

 while the memoirs of Gegenbaur on the carpus, on the shoulder- 

 girdle, and on the skulls of Selachian fishes, and Kitchen 

 Parker's memoirs devoted to mature forms, may be taken as 

 examples that morphological problems suggested by adult com- 

 parative anatomy have not lost their attraction to men capable 

 of elaborate original research. And I the more willingly select 

 the names of these two writers, because on one subject on which 

 they have written, the shoulder-girdle, I am compelled to differ 

 from their conclusions and to adhere rather to those of Owen, 

 so far as the determination of the different elements in fishes is 

 concerned ; and by stating this (although the subject cannot be 

 now discussed) I am enabled to illustrate that the appreciation 

 of the value of elaborate and painstaking work is a matter 

 totally distinct from agreement with the conclusions which may 

 be arrived at in the investigation of complicated problems, 

 although wisdom and penetration as to these must ever command 

 admiration. 



But when one looks back on the times of Meckel and Cuvier, 

 and on the activity inspired by the speculations of the much- 

 abused Oken, the writings of Geoffroy St.-Hilaire, the less 

 abstrusely speculative part of the works of G. C. Carus, and 

 the careful monographs of many minor writers ; when one re- 

 flects on the splendid grasp of Johannes Miiller, and thinks of 

 the healthy enthusiasm created in this country for a number of 

 years by Owen's " Archetype and Homologies of the Vertebrate 

 Skeleton," and then contemplates the state of vertebrate mor- 

 phology at the present moment, it seems to me that its homolo- 

 gical problems and questions of theoretical interest do not 

 attract so much attention as they did, or as they deserve. 



77^,? Origin of Species by Natural Selection. 



There can be no doubt that a great and curious influence has 

 been exercised on morphology by the rise of the doctrine of 

 the origin of species by natural selection. Attention has been 

 thereby directed strongly for a number of years to varieties, 

 and probably it is to this doctrine that we owe the larger 

 number of observations made on variations of muscles, nerves, 

 and other structures. Particularly elaborate have been the 

 records of muscular variations, very praiseworthy, interesting to 

 the recorders, very dry to most other people, and hitherto, so 

 far as I know, barren enough of any general conclusions. So 

 much the more credit is due to those who have worked steadily 

 in faith that beauty will emerge to gild these results some day. 



But the doctrine of natural selection has had a further effect 

 in anatomical study, aiding the reaction against the search for 

 internal laws or plans regulating the evolution of structures, and 

 directing attention to the modifying influences of external 

 agencies. This effect has happened naturally enough, but it has 

 been far from just ; rather is it a pendulum-Hke swing to another 

 extreme from what had previously been indulged in. The 

 doctrine of natural selection starts with the recognition of an 

 internal formative force which is hereditary ; and in the develop- 

 ment of the doctrine, the limits of hereditary resemblance have 

 een greatly studied ; and further, it will be observed that one 



of the fundamentals of the doctrine is, that the formative force 

 alters its character gradually and permanently when traced from 

 generation to generation in great tracts ot time. Now I am 

 not going to enter on a threadbare discussion of the origin of 

 species in this company ; suffice it to say that, while the existence 

 and extensive operation of such a thing as natural selection 

 seems to have been convincingly proved, it is a very different 

 thing to allege that it has been the sole, or even the principal 

 agent in producing the evolutions of living forms on the face of 

 the earth. So far as anatomy is concerned, it is a secondary 

 matter whether the link between the members of the evolving 

 hosts of life have been genetic or not. But I wish to point out 

 that, even pushing the Darwinian theory to the utmost possible 

 extreme, the action of external agents infers the existence of 

 something acted on ; and the less directly they act, the more 

 importance must be given to the hereditary or internal element. 

 We are therefore presented with a formative force, which ex- 

 hibited itself in very simple trains of phenomena in the first 

 beginnings of life, and now is manifested in governing the 

 complex growth of the highest forms. We are set face to face 

 with that formative force, and are obliged to admit its inherent 

 capability of changing its action ; and that being the case, is it 

 more of an assumption to declare that the changes are all 

 accidental and made permanent by accident of external circum- 

 stances, or to consider that it has been the law proper to this 

 force to have been adequate to raise forms, however liable to 

 modification by external circumstances — to raise them, I say, 

 from the simple to the complex, acting through generations on 

 the face of the earth, precisely as it acts in the evolution of a 

 single egg into an adult individual? This is that formative 

 force which has been elaborately shown by Mr. Darwin, in 

 launching his theory of " pangenesis," not only to be conveyed 

 through whole organisms and their seed, but to pervade at all 

 times the minutest particles of each ; and I merely direct atten- 

 tion to the fact that its extension over the whole history of life 

 on the globe must be granted, and ask if, in the range of forms 

 which furnish at the present day an imperfect key to the ages 

 which are past, there is not exhibited a development comparable, 

 in its progression to definite goals, with what is shown in the 

 life of a single plant or animal. For my own part, I am fully 

 convinced of a unity of plan running through animal forms, and 

 reaching, so far as the main line is concerned, its completion in 

 the human body. I confess that I think that there is evidenc ; 

 that animal life has reached its pre-ordained climax in humanity ; 

 and I cannot think it likely that, as myriads of years roll on, 

 descendants differing ?« toto from man will be developed. To 

 argue the subject would be to enter on the largest subjects of 

 morphological anatomy, and on speculations on which agreement 

 could not be expected. Even, however, in the nature of the 

 variations in the human race there seems to be some evidence 

 that the progress of evolution is to be traced from man, not to 

 other animal forms yet to appear, but, through his physical 

 nature, into the land of the unseen. Those variations, keeping 

 out of view differences of bulk and stature, which appear to 

 have some relation to geographical position, are principally to 

 be found in the head, the part of the body most closely con- 

 nected with the development and expression of the mental 

 character ; and I may mention that when, some years ago, my 

 attention was directed to the variations of the skull, the only 

 part whose variations in different races I have had opportunity 

 of studying with any degree of minuteness, I became satisfied 

 that in uncivilised races there might be distinguished skulls 

 which had undergone hereditary degeneration, others which had 

 reached the most advanced development possible for them, and 

 a third set, notably the Kaffirs, with large capabilities for im- 

 provement in the future. Indeed it is beyond doubt that there 

 is a limit for each type of humanity beyond which it cannot 

 pass in the improvement of the physical organisation necessary 

 for mental action. 



There are also some curious indications in human structure of 

 the formative force nearing the end of its journey. In the 

 details of the skeletons of other animals one sees the greatest 

 precision of foim ; but there are various exceptions to this neat- 

 ness of finish in the skeleton of man, and they are found in 

 parts specially modified in connection with the peculiarities of 

 liis development, and not requiring exactness of shape for 

 physiological purposes ; while, on the other hand, physiogno- 

 mical mould and nicety of various physiological adaptations are 

 found in perfection. Look at the variations in the breast-bone, 

 especially at its lower extremity, which is never shapely, as it 

 is in the lower animals. Look at the coccygeal vertebrae ; they 



