February i6, 191 i] 



NATURE 



511 



iorm of an animal is in great measure kept up by the 

 same identical means by which a true hreed. is produced. 

 The original form of a species is unquestionably better 

 adapted to its natural habits than any modification of that 

 form; and, as the sexual passions excite to rivalry and 

 .<onflict, and the stronger must always prevail over the 



• weaker, the latter, in a state of nature, is allowed but 

 -few opportunities of continuing its race. In a large herd 



of cattle, the strongest bull drives from him all the younger 

 and weaker individuals of his own sex, and remains sole 

 master of the herd ; so that all the young which are pro- 

 educed must have had their origin from one which possessed 

 the maximum of power and physical strength, and which, 

 consequently, in the struggle for existence, was the best 

 Jible to maintain his ground and defend himself from every 

 enemy. In like manner, among animals which procure 

 their food by means of their agility, strength, or delicacy 

 of sense, the one best organised must always obtain the 

 greatest quantity, and must, therefore, become physically 

 the strongest, and be thus enabled, by routing its 



.opponents, to transmit its superior qualities to a greater 

 number of offspring. The same law, therefore, which was 



. intended by Providence to keep up the typical qualities of 



..a species, can be easily converted b)' man into a means 

 of raising different varieties; but it is also clear that, if 



man did not keep up these breeds by regulating the sexual 

 intercourse, the}' would all, naturally soon revert to the 



■original type. Farther, it is only on this principle that 

 we can satisfactorily account for the degenerating effects 

 said to be produced by the much censured practice of 



* breeding in and in.' There would almost seem, in some 

 .species, to be a tendency, in every separate famih', to 



some particular kind of deviation, which is only counter- 

 acted by the various crossings which, in a state of nature, 

 .must take place, and by the above-mentioned law, which 

 causes each race to be chiefly propagated by the most 

 typical and perfect individuals " (pp. 45—46).' 



On the suggestion of Prof. Cossar Ewart, the above 

 quotation was submitted to Mr. Francis Darwin, who has 

 Jiindly informed me that he agrees with my remarks in 

 general, but is unable to slate definitely the identity of the 

 author. 



In his introduction to the " Origin " Darwin notices 

 several such " anticipations," but no reference is made to 

 Blyth's name in this connection. 



It seems indeed strange that Darwin should have been 

 unacquainted with this article, and, what appears stranger 

 still, that Blyth himself should have failed to direct atten- 

 tion to his paper, or that there should be no mention of 

 these passages in either Darwin's or Blyth's corre- 

 spondence. Mr. Francis Darwin has, however, indicated 

 (" More Letters," i., p. 62) that much of Daiwin's corre- 

 spondence with Blyth has not been forthcoming. This is 

 to be regretted. 



Curiously enough, in a letter to Lyell, Darwin says : — 



BUth says (and he is in many respects a good judge) 

 that his ideas on species are quite revolutionised. ..." 

 <" Life and Letters," ii., 1887, p. 316.) 



At this juncture the question naturally arises, viz., Is 

 the Edward Blyth of the article the Edward Blyth of 

 Calcutta? On turning to Grote's "memoir" (Journal 

 Asiatic Soc. Bengal, .August, 1875, part ii., supplement), 

 we find (p. 5) that Blyth contributed to both Louden 's and 

 Charles worth's series of the Magazine of Natural History 

 from the year 1833. From the titles of the various articles 

 which appear under Edward Blyth's name in Louden 's 

 Magazine, there is no evidence to indicate that all these 

 contributions did not originate from the same writer. On 

 Grote's evidence we are therefore justified in concluding 

 .that our author is the naturalist who afterwards made 

 himself famous by his writings on, and profound know- 

 ledge of, the mammals and birds of India. Moreover, this 

 conclusion is substantiated by our author's address, given 

 in the same volume of Louden in several instances as 

 *' Tooting, Surrey," and we learn (" Diet. National Biog., 

 London, 1886, vol. v., p. 276, art. Blyth, Edward) that 

 Blyth purchased a druggist's business at Tooting on 

 .coming of age. 



Mr. J. Ritchie, of the Royal Scottish Museum, has 

 suggested to me that Blyth, in 1859, may quite easily have 

 forgotten what he had w^ritten twenty-four years 

 1 The italics in thi."; quotation are Blyth's. 



NO. 2155, VOL. 85] 



previously, the more so as he failed in the true application 

 of his " principle." The association of his ideas with 

 those of Darwin would, therefore, be incomplete or 

 entirely wanting. 



Though Blytfr seems clearly to have recognised the prin- 

 ciple of natural selection, he fails in its true application 

 in that he regards his " principle " as operating for the 

 conservation rather than the progression of the type, 

 whereas the two really go hand in hand, thjg one being 

 a. complement of the other in the successive stages of 

 evolution. Moreover, proof of Blyth's inability to recc^- 

 nise the logical issue of his theory is exhibited in some 

 of his remarks, which appear to disagree, or are incom- 

 patible with, one another. For instance, it is hard to 

 reconcile the sentence commencing " Farther," and end- 

 ing '• breeding in and in," with some of his previous state- 

 ments. 



Blyth was a staunch supporter of Darwin's views, and 

 his eajly theorisings are of interest in connection with his 

 projected work on " The Origination of Species," which, 

 however, was never completed, even in manuscript form 

 (Grote, loc. cit., p. xiv). H. M. Vickers. 



81A Princes Street, Edinburgh, February 3. 



The Sailing-Flight of Birds. 



In N.\ture of February 2, Mr. Mallock remarks that 

 the skimming of some birds near the surface of the waves, 

 where the variations in the velocity of the wind are great, 

 may be dependent only on the inequalities of a horizontal 

 breeze, and that an upward current is not absolutely 

 necessary. My own observations have led me to the con- 

 clusion that whenever a bird glides for any distance with- 

 out losing altitude he is, no less than the soaring kite 

 or eagle, utilising an upward current of air. But it is 

 possible that Mr. Mallock ma}- be thinking of the albatross, 

 who is perhaps without peer in his power of profiting by 

 the vagaries of the wind. Unfortunately, I have had no 

 opportunities of observing the albatross, and from those 

 who have I get very conflicting accounts, some maintain- 

 ing that he will glide for long distances under conditions 

 which make it almost certain that the wind is horizontal, 

 others holding that, though he brings the art to greater 

 perfection, he does nothing different in kind from what 

 the gull, that hangs with outstretched wings over the stern 

 of a steamer, is able to achieve. 



My object in writing this is to urge any of your readers 

 whose good fortune gives them opportunities of watching 

 the albatross on the wing to make careful observations on 

 this very interesting subject. F. W. He.\dlev. 



I AGREE with Mr. Headley that obser\'ations of the 

 various conditions under which flight with fixed wings can 

 be accomplished are desirable, but it is quite as important 

 to determine the motion of the air in any particular case 

 as to observe the behaviour of the bird. 



In the case of a bird skimming close to the surface of 

 waves, the action is presumably that sketched below. To 



appreciate this properly, regard must be had to the vertical 

 motion of the air in respect to time as well as to the wave 

 surface. It is assumed that the speed of the wind is 

 greater than that of the waves, and that the bird is flying 

 to windwards. In these circumstances, the mean velocity 

 of the air is less in the lee of each wave-crest than it is 

 on the windward slope (indeed, when the waves are steep, 

 the flow on the lee side may be reversed). 



If a bird follows the course indicated by the dotted 

 line, it gains, not only from the ascending current off the 

 windward slopes, but also from the increased velocity it 

 can acquire by dropping to a low level in the slower wind 

 to the leeward of them. 



The question of possible flight by variations of hori- 

 zontal velocity has been treated by Lord Rayleigh and Mr. 

 R. E. Froude. A. Mallock. 



In the flight of birds, besides the change in the inclina- 

 tion of the wing planes noted by the Rev. R. .\bbay in 

 Nature of February 9, there must surely be some move- 

 ment either of the wing, tail, or body which takes the 

 place of the screw of the aeroplane. The seagull, for 



