March 23, 1^99] 



NA TURE 



487 



twenty five years for man's cessation of growth is therefore only 

 an average one, in introducing that number as a factor of the 

 curve, I thought that it would be manifestly an error to take 

 examples of exceptionally long lives, when striking an average 

 for length of life. In the curve as published in Nature (which, 

 although published somewhat before my communication to the 

 Laih'tt, is really a revised curve), I reduced the age of man 

 from eighty to seventy-five years from considerations such as I 

 have just mentioned. Even seventy- five years is somewhat 

 greater than the expectation of life given in Bourne's " Manual," 

 for those who have| completed the first half-century of their 

 existence. The age given by Buffon, and quoted by Mr. Bell, 

 is undoubtedly far too long. Similar considerations from some 

 fresh data induced me to reduce the mean lifetime of the 

 domestic mouse from four and a half years to four years, as 

 noticed by Mr. Bell. W. Ainslie Hollis. 



Il.'ve. 



Barnes' " Plant Life." 



/it ic centrosomes : 



Poor misguided Prof. Zacharias ! With absolutely no provo- 

 cation, he now departs from " the almost universal consensus of 

 opinion among good botanists " by saying of centrosomes (Bol. 

 Zeit., 572: 6, 1899): 



" However, on an unprejudiced consideration of the literature 

 involved, one may consider it not impossible that, on renewed 

 search, the centrosomes will finally be again discovered where, 

 for the present (' mark, Jew ! '), they have been missed." 



And Guignard ! What a stupid he is to repeat in greater 

 detail the blunder of figuring and describing those "discredited'' 

 centrosomes when a.\\ good botanists (who swear by Strasburger 

 and his young American students) know that there are no such 

 things ! And to think of his calling them " Les centres cine- 

 tiques chez les vegetaux " (see Annates dcs Sci. NaturelUs, Bot., 

 viii. 5, 177-220, 1S98), as though they were common ! How 

 "amazingly behind the times" ! 



But there must be more reason than assigned for designating 

 " Plant Life " as "amazingly behind the times." Prof. Barnes 

 would really be under obligations to the reviewer if he could 

 find lime to indicate by number of p.age or paragraph (doubt- 

 less marked as the book was yawned over) the statements to 

 which he considers this phrase applicable. This request is 

 made in all sincerity, and in the hope that the number of these 

 passages will not be so great as to make it presumptuous in ii 

 demands upon the reviewer's time. '" " t!.,.^,ui: 



C. R. B.\KNES. 



The reviewer cannot help regretting the evident pain which 

 his remarks (vol. Iviii. p. 519) have caused Prof. Barnes, though 

 the latter can scarcely seriously believe that his arguments and 

 assertions meet the original objections to which he has taken 

 exception. 



Prof. Barnes appears to be particularly aggrieved at the refer- 

 ence made to the figures and account of centrosomes, but his 

 own explanations merely serve to give force to the reviewer's 

 contention that they ought not to have found a place in an 

 elementary book at all. 



If the best final reply he can make is to quote the opinion of 

 Zacharias to the effect that "it is not impossible that on renewed 

 search the centrosomes will finally again be discovered," he 

 should see that his case is parlous indeed. He has, in fact, 

 cast a far greater slur on his own critical judgment than the re- 

 viewer would have ventured to do. His further quotation of 

 Guignard's recent work might perhaps be regarded as some- 

 what t-.v parte, even had that investigator reiterated the old 

 statements on which Prof. Barnes' account was based. As a 

 matter of fact he does not do so, and his silence tells against our 

 author. 



The somewhat contemptuous reference to Strasburger (who 

 is nevertheless /aczV« princeps amongst botanical cytologists) and 

 to those younger American botanists whose reputations, paei 

 Prof. Barnes, are largely founded on the splendid results achieved 

 by them at Bonn, are scarcely calculated to increase one's regard 

 for Prof. Barnes' power of discrimination. 



Prof. Barnes appears to be quite un.able to realise the degree 

 of mental confusion which would be the inevitable lot of a 

 student endeavouring to deal with the account given by him of 

 the movement of water in plants. Iti one place (§ 204) root- 

 pressure is spoken of as the force which causes the movement 

 from the root to the evaporating surfaces of the leaves ; but in 

 § 207 the author rightly remarks that root-pressure is practically 



NO. 1534, VOL. 59] 



inoperative at the time when transpiration is most active. But 

 he goes on to add that " recent experiments " indicate that the 

 negative pressure of the gas-bubbles in the tracheids maybe "a 

 very important, or even the chief factor in lifting the water." 

 After this one ceases to be surprised that no mention is made of 

 the conclusions reached by Dixon and Joly, or by Askenasy ! 



But Prof. Barnes asks for further evidence for the reviewer's 

 unfavourable opinion of the book. Only a few instances need 

 be mentioned here, for if "this request is made in all sincerity," 

 the author's own friends will easily supply more. 



In a work of this kind, it is astonishing to find no mention of 

 the occurrence of motile antherozoids amongst the lower phan- 

 erogams, which is perhaps the most important of all recent 

 botanical discoveries — important for the student as clearly 

 showing the connection between the higher and lower plants. 



The account given in § 143 of annual rings is so preposterous 

 as to call for no further comment. 



The respiratory quotient of the ordinary plant is still given as 

 unity, when, as a matter of fact, it is nearly always other than 

 I in growing plants. 



The statement that "true geotropic curvatures are brought 

 about by the acceleration of the growth of the irritable cells " is, 

 as it stands, absurd, for it involves no necessary curvature 

 at all. 



A student reading the account given in § 230 would naturally 

 fall into the error of concluding that all the rays of light 

 absorbed by chlorophyll are equally active in promoting 

 a.ssimilation. 



In view of the evidence here adduced, at [Prof. Barnes' own 

 request, the reviewer considers that his judgment of the book 

 was by no means unduly harsh or severe. 



The Reviewer. 



Optical Experiment. 



Being driven past a row of trees, I noticed that their inter- 

 mittent shadow on the closed eye-lids gave rise to a vivid chess- 

 board pattern of red and black squares arranged horizontally and 

 vertically. These were perfectly regular, each being equil to 

 about one-twelfth of an inch at ten inches distance. Waving 

 the open fingers in front of the closed eye-lids exposed to the 

 sun gave the pattern fairly well, but better by flashing the sun's 

 rays across the lids by means of a vibrating hand-mirror. I see 

 about seven or eight squares each way, the outer ones not well 

 defined ; but a younger inan, who was not told what to expect, 

 described them as more numerous. 



What structure in the eye gives rise to the phenomenon ? It 

 is not caused by the eye-lids, beca.ise a piece of tissue-paper can 

 be substituted, the eyes then being open. If the paper is white 

 the squares are white and black. The pattern occupies the 

 centre of the field of each eye. Thom. D. Smeaton. 



Adelaide, South Australia, February 6. 



A SEISMOLOGICAL OBSERVATORY AND ITS 

 OBJECTS. 



TEN years ago seismologists practically confined their 

 attention to the movements of the ground which 

 could be felt. In Italy and Japan, where these were 

 frequent and sometimes violent, they attracted serious 

 attention ; whilst in Britain, where earth tremors were 

 comparatively unknown, any suggestion that this country 

 should establish a seismological observatory might only 

 have cast doubts upon the mental balance of its author. 

 At that time it was popularly supposed that in our 

 islands earthquakes were of such rare occurrence that a 

 special establishment for seismological investigations 

 was unnecessary. Seisinology, however, like several 

 other sciences, has in a comparatively short period 

 advanced with strides, and now stands as foster-mother 

 not only to a Romulus and Reinus, but also to a number 

 of other children all filled with promise. 



Now we know that in England, or in any other non- 

 seismic region on the surface of the globe, at least 

 seventy unfelt earthquakes, each of which have durations 

 varymg between twenty minutes and several hours, may 

 be recorded yearly. The probability is that these rtiove- 

 ments are transmitted from their origins as compressional 



