436 



NATURE 



[March io, 1892 



self-taught, and executed fantasias chiefly remarkable 

 for their disregard of every known rule of composition. 

 Touches of family affection here and there relieve the 

 intellectual pre-occupation lending its prevalent stamp to 

 the Huygenian correspondence. One likes the great 

 man better for his questions about the walking and talk- 

 ing achievements of his little niece, Gertruid Doublet, 

 than for having solved the problem of the centre of 

 oscillation, or discovered the isochronism of the cycloid. 

 The maiden's modest proficiency was not carried to a 

 high pitch. She died in 1665, at the age of four. 



In the way of astronomy, Huygens did nothing of 

 much moment during this interval. Admonished by 

 Boulliaud of its visibility, he made his first observation 

 of Mira Ceti at the Hague, on August 15, 1662, when it 

 was nearly as bright as k Ceti (fifth magnitude). The next 

 account of the star is on September 15, three weeks at 

 least after a maximum ; and its declining state seemed to 

 Boulliaud marked by the flaring and flashing of its light, 

 as if in truth a semi-extinct conflagration revealed itself 

 in his telescope. " C'est un spectacle," he adds, " k faire 

 ddsespdrer Aristote et ses disciples " (" Corr. de Huygens," 

 t. iv. p. 231). Occasionally, too, Huygens pointed out 

 the sustained conformity of the Saturnian appearances to 

 his theory of them. The logic of fulfilled prediction had, 

 indeed, by this time persuaded all but the few outstanders 

 always averse to conviction by truth, that the hypo- 

 thetical and the real systems were practically identical. 



The two years embraced by the present section of this 

 grand work were exceedingly peaceable ones. The 

 gates of the Temple of Janus in the republic of letters 

 remained fast shut as they slipped by. Scarcely a ripple 

 of contention stirred. Everyone was in good humour, 

 and carped at his rival's doings only sotto voce — a state 

 of things peculiarly agreeable to our Batavian philo- 

 sopher, who loved not to have his meditations broken in 

 upon by the shrill outcries of wounded self-love. Could 

 it but have continued ! But that was not to be. 



A. M. Clerke. 



THE HORSE. 



The Horse : A Study in Natural History. By William 

 Henry Flower, C.B., F.R.S., &c. (London: Kegan 

 Paul, 1891.) 



IF there be a fault in the admirable little volume which 

 Prof. Flower has contributed to the " Modern 

 Science " series, it is that the author too cautiously with- 

 holds his opinion on certain broad biological questions 

 in which not only naturalists but the general reading 

 public are just now specially interested. Early in the 

 first chapter, for example, we read : — 



" In many organs, but especially in the limbs and 

 teeth, we find the strongest evidence of two opposing 

 principles striving against each other for the mastery in 

 fashioning their form and structure. We find heredity, 

 or adherence to a general type derived from ancestors, 

 opposed by special modifications of or derivations from 

 that type, and the latter generally getting the victory, 

 although in the numerous rudimentary structures that 

 remain there is significant evidence of ancestral conditions 

 long passed away. The various specializations, evidently 

 in adaptation to purpose, will be thought by many to be 

 the result of the survival, in the severe struggle for exist- 



NO. I I 67, VOL. 45] 



ence, of what is best fitted for the purpose to which it is- 

 to be applied. This may or may not be the explanation, 

 but the interest of the study of such an animal as the 

 horse will be increasd tenfold by the conviction that there 

 is some true and probably discoverable causation for all 

 its modifications of structure, however far we may yet be 

 from the true solution of the methods by which they have 

 been brought about." 



Here natural selection is not so freely and fully ac- 

 cepted as many would wish. But the grounds of doubt 

 are not indicated. On the other hand, use-inheritance 

 fares worse. It is not so much as hinted at. It is well 

 known that there are, especially in America, biologists of 

 standing who contend that differentiations of structure 

 are largely due to a Lamarckian factor in evolution ; and 

 they adduce specialization of tooth-structure and of limb- 

 structure as evidence of the inherited effect of mechanical 

 strains and stresses. Now, in the horse specialization in 

 teeth and limbs has been carried far. The general public 

 and not a few biologists would, we think, have been glad 

 to learn the opinion of the Director of our National 

 Museum as to the scientific value of such views in so far 

 as they apply to the subject of his " study." 



On another point of very general interest Prof. Flower 

 does, however, express an opinion. It has been suggested 

 that the horse has been separately evolved in America 

 and in Europe through a parallel but not identical series 

 of ancestral forms. The evidence for this hypothesis is 

 generally regarded in this country as insufficient, and it 

 is now held that the horse was probably evolved on the 

 Western Continent. This is the view adopted, with his 

 accustomed caution, by the author of this book. 



" It is," he says, " by no means impossible that America 

 may have been the cradle of all the existing EquidcE, as 

 it seems to have been of such apparently typical Old 

 World forms as rhinoceroses and camels, and that they 

 spread westward by means of the former free communi- 

 cation between the two continents in the neighbourhood 

 of Behring's Straits, and, having prevailed over the 

 allied forms they found in possession, totally disappeared 

 from the country of their birth until reintroduced by the 

 agency of man. This supposition, based upon the great 

 abundance and variety of the possible ancestral forms of 

 the horse which have lately been discovered in America, 

 may be at any time negatived by similar discoveries in 

 the Old World, the absence of which at the present time 

 cannot be taken as any evidence of their non-existence.'* 



The discovery in the Old World of ancestral Perisso- 

 dactyles, in numbers at all comparable to those which 

 have been found in America, would no doubt throw a 

 flood of light on difficult questions of evolution and dis- 

 tribution. If, as Madame Marie Pavlow has suggested, 

 Sir Richard Owen's Hyracotherium is (perhaps) identical 

 with Prof. Co^&' s Phenacodus, similar genera have existed 

 on either side of the Atlantic since early Eocene times. 

 In both continents these early forms presumably left de- 

 scendants. Between the primitive Phenacodus and the 

 existing horse there are many intermediate forms, some 

 of which seem to be generically identical in America and 

 in Eurasia. Have there, then, been many successive 

 migrations from the West ? Have there been counter- 

 migrations from East to West ? What have been the 

 relations between the indigenous descendants oi Hyraco- 

 therium and the successively immigrant descendants of 

 Phenacodus ? These and other questions may possibly 



