April 24, 1890] 



NATURE 



585 



adjustment," nor any amount of change as to "shape," deserves 

 to be regarded as " any important result " ? Must we not rather 

 conclude that when he first wrote upon "the state of panmixia," 

 he had not sufficiently considered the subject ; and, in now 

 endeavouring to trim, ends by contradicting himself? 



The only issue being as to whether panmixia is itself a cause, 

 or merely the precedent condition to the occurrence of a totally 

 different cause, nothing more remains to be said. As a result 

 of his further consideration, Prof. Lankester now admits "it is 

 clear" that, " without economy of growth," panmixia is a cause 

 of degeneration where " shape" and " structure" are concerned. 

 And, when he considers the matter a little more, he will doubt- 

 less perceive the contradiction in saying that, where degeneration 

 as to "size "is concerned, "it is absurd to attribute the result, 

 or any proportion of it, to the panmixia or cessation of selection 

 alone." Variations round an average mean occur in "size" or 

 "bulk," just as they do in "shape" and "structure": there- 

 fore, if on this account panmixia is conceded to be a true cause 

 of degeneration as regards the latter, it must likewise be so as 

 regards the former. The fact that in the former case — as I 

 showed in 1874— it must always be more or less associated with 

 the economy of growth, is no proof that it then loses its due 

 "proportion" of causal agency; while, with the now single 

 exception of Prof. Lankester, everyone who has since writien 

 upon this "principle" takes the same view as I did — viz. that 

 the phenomena of " dwindling " in our own domesticated ani- 

 mals furnish as good evidence of the operation of panmixia as 

 is furnished by the other forms of degeneration to which he now 

 alludes. Therefore, if he really believes it is in this case " absurd 

 to attribute the result, or any proportion of it, to the panmixia," he 

 becomes opposed, not only to me, but to Galton, to Weismann, 

 to Poulton, and to everybody else who has ever considered the 

 subject. In short, it is now a matter of general recognition 

 that what he calls my " unreal separation between ' cessation of 

 selection ' and ' reversal of selection,' " is a separation so funda- 

 mentally real, that it is the means — and the only means— of 

 abolishing the evidence of Lamarckian factors where this once 

 appeared to be most conclusive ; seeing that " with highly-fed 

 domesticated animals there seems to be no econofny of gi-oivth, nor 

 any tendency to the elimination of superfluous details." ^ 



April 19. George J. Romanes. 



In Nature of April 3 (p. 511) Mr. Herbert Spencer suggests 

 an interesting subject for discussion on the effects of use and 

 disuse of organs, asking for an explanation on the theory of 

 panmixia of the well-known tendency of domesticated animals to 

 droop the ears. Many of the ruminants in a wild state have iheir 

 ears set on horizontally with an inclination to droop ; for 

 instance, the gnu, sable, antelope, zebu, gaur (Central India), 

 Cape buffalo, &c. The American bison has completely drooping 

 ears ; there is also at the Natural History Museum, South 

 Kensington, in Case 57, a specimen of a smooth-haired 

 sheep from Turkey in Asia, Ovis aries, which has dependent 

 ears. Pathologically, though as yet not physiologically proved, 

 the discussion of the transmission of acquired characters possesses 

 a deep interest. 



Evolution seems impossible without variation, and until the 

 latter can be explained on other grounds than those of the in- 

 heritance of accumulated minute changes in character acquired 

 through ages of slowly varying climate and conditions of life, 

 preserved by natural selection, this transmission would seem a 

 reasonable conclusion so long as the characters acquired were 

 of service to the inheritor in the struggle for existence. 



Though Weismann disbelieves most of the evidence Darwin 

 collected on heredity, and doubts the possibility of the com- 

 munication of external influences by the somatic cells to the 

 germ cell, he suggests no other hypothesis to account for the 

 phenomena of change, beyond the vague expression "predis- 

 position of the germ-plasm." R. Haig Thomas. 



April 5. 



* Darwin, " Variation. &c.," ii. p. 289. Seeing the importance of "the 

 idea of panmixia" in this connection, I must still be permitted to regard it 

 ^, ,.""'?'''""^'^ " '''*' " ^^^ "°' present to Mr. Darwin's mind before the 

 pubhcation of his last edition of the "Origin of Species." But this does 

 not mean, as Prof. Lankester " affects to suppose," that I regard the un- 

 fortunate nature of such a circumstance as due to the fact that I happened 

 Jp OS the first who perceived it. One can only assign so petty a form of 



badinage" to ihe same argumentative level as "pointing out the over- 

 sight " that in my first letter I "omitted to credit Mr. Darwin with the 

 recognition of the economy of growih." Prof. Lankester has committed 

 about as grave an oversight in his own letter, by omitting to credit Mr. 

 Darwin with the recognition of natural selection. 



The "Rollers " of Ascension and St, Helena. 



You probably know that the United States Scientific Expedi- 

 tion under Prof Todd has had occa.sion to stop here during the 

 past two weeks. I have resided during this time continuously 

 at the signal station on Cross Hill (altitude 870 feet), studying 

 the clouds and winds with many important results. I have had 

 an excellent opportunity to observe the "rollers" for which 

 Ascension and St. Helena are famous, and I have been able to 

 demonstrate convincingly to myself their nature and origin. I 

 should be obliged to anyone who will tell me whether my 

 following views have perhaps been arrived at by previous 

 observers. 



The south-east trade blows with very various intensities over 

 different parts of the South Atlantic, and the regions of light 

 trade, no trade, fresh and strong trade, vary from day to day, as 

 shown by comparing the logs of vessels. A limited region of 

 strong south-east trade is a region whence spreads in all directions 

 the corresponding strong south-east swell of the ocean surface — 

 very distant storm winds or very near regions of high south-east 

 winds produce similar results on the ocean swell : the locality of 

 these winds will determine whether any point shall be experienc- 

 ing a light or heavy swell. What causes the variations in the 

 south-east trades, and in what direction the regions of strong 

 trade move, are questions for further study. My present data 

 would show that these latter regions move against the trade 

 winds, i.e. from Ascension towards St. Helena, but there need 

 be no uniformity in this respect. 



Now if a south-east swell surrounds such an island as Ascension 

 it is not directly felt on the lee side, but the long rectilinear 

 swells, that advance faster in deep than in shoal water, are seen 

 from my elevated station to assume the new curved shapes that 

 result from the retardations on the shoals. So that finally in 

 typical cases we have off the lee of the i.'-land a series of cross- 

 ing and interfering swells producing at one point a quiet spot, at 

 the next a double .swell and great breakers. 



The rollers are a magnificent example of deflection by shoals, 

 and of interference and of composition of waves. Their severity 

 at St. Helena and Ascension is apparently due to the proportions 

 of the dimensions of the swell to that of the islands, just as in 

 the interference phenomena of sound and light everything 

 depends on the size of obstacle and length of wave. I have a 

 number of measures that will, I hope, enable me in the future 

 to give more accurate details, but for the present I can only 

 inquire as to the bibliography of the subject. The correct 

 explanation of the rollers, and of the swell on the West African 

 coast, will undoubtedly lead us to further steps in marine 

 meteorology. Cleveland Abbe. 



U.S.S. Pensacola, Ascension, April 2. 



Self- Colonization of the Coco-nut Palm. 



With reference to Mr, Hemsley's note on this subject to 

 Nature (p. 537), I regret to have to inform him that the two 

 young palms found on Falcon Island were placed there by a 

 Tongan chief of Namuka, who, in 1887, had the curiosity to 

 visit the newly-born island, and took some coco-nuts with him. 

 This information I received from Commander Oldham, who had 

 been much interested at finding these sprouting nuts at some 12 

 feet above sea-level and well in from the shore of the island, but 

 who found out the unexpected facts in time to save me from 

 making a speculation somewhat similar to Mr. Hemsley's. 



W. J. L, Wharton. 



Nessler's Ammonia Test as a Micro-chemical 

 Reagent for Tannin. 



In most cases the presence of tannin is immediately shown by 

 all the ordinary reagents used by the botanist for its discovery. 

 This does not happen sometimes, however ; as, for instance, in 

 the tannin-cells found in the epidermis on the dorsal side of the 

 leaves of some plants. As a good typical example the common 

 primrose may be cited. Of all the ordinary tests, including 

 iron salts, potassium bichromate, Moll's test (copper acetate and 

 iron acetate), ammonium molybdate, and osmic acid in i per 

 cent, solution, the latter alone acts immediately upon the 

 tannin in the primrose leaf's epidermis. It may hence be worth 

 while recording the discovery of a second reagent capable of 

 acting rapidly and effectively ; and one which is easily made and 

 will keep for some time should be especially valuable Such a 

 reagent is Nessler's test for ammonia. 



