8o 



NATURE 



\_Nov. 25, 1880 



this he is supported by such authorities as Sachs and 

 Strasburger ; but it is impossible to say anything at 

 present as to the form and arrangement of the micellre of 

 protoplasm beyond this, that they do not so act upon 

 polarised light as to suggest that they are crystalline. 

 Full details on this subject, as well as a vast amount of 

 other information, is given in the treatise on the Micro- 

 scope (second edition, 1877), which Niigeh wrote together 

 with Schu-endener ; fortunately an English edition of this 

 important work may soon be expected to appear. 



In tracing the development of Nageli's theory, it has 

 been necessary to depart from the chronological order of 

 his works. In the years between 1S5S and 1S68 he 

 published his Beitrcigc znr ivissenschaftlichcn Bolanik, 

 which include several important works, for the most part 

 anatomical. In the first number there is an elaborate 

 paper on "The Arrangement of the Fibro-vascular Bundles 

 and the Mode of Growth in the Stem and Root of Vas- 

 cular Plants," which is important as containing a purely 

 morphological classification of the different forms of tissue 

 of which these organs consist. This is followed by a 

 detailed account, in the fourth number, of the mode of 

 growth in thickness and of the arrangement of the fibro- 

 vascular bundles in the stem among the Sapindacea;, and 

 this number also contains Nageli's well-known investiga- 

 tion into the mode of development and growth of roots, in 

 which Leitgeb was associated with him. This publication 

 has a further interest connected with it, in that Schwen- 

 dener's first papers on what is now known as his Lichen- 

 theory appeared in it. 



During this period Niigeli frequently contributed papers 

 (the Bofanische MittJu-ihingeii) on a variety of subjects 

 of botanical interest to the Proceedings of the Bavarian 

 Academy, an activity which continues up to the present 

 time. Allusion has already been made to some of these, 

 and it would be worth while, did space permit, to give an 

 account of most of them. Among the more important 

 the following may be mentioned : — '" On the Sieve-Tubes 

 of Cucurbita," " On the Proteid Crystalloids of the Brazil- 

 nut," " On the Development of Varieties," "A Theory of 

 Hybridisation.'' Of late years Nageli has turned his 

 attention more especially to the study of the chemical 

 composition and vital processes of the lower Fungi, such 

 as Yeast and Bacteria. Among the interesting results 

 obtained is the discovery, in yeast-cells, of a ferment 

 (invertin) which converts cane- into grape-sugar, and of 

 peptones. But the real importance of these researches 

 only became apparent on the publication of two larger 

 works, viz. : " The Lower Fungi in their Relation to In- 

 fectious Disease" (1877), and " A Theory of Fermenta- 

 tion" (1879). It is of course impossible to give here any- 

 thing like a satisfactory account of the contents of these two 

 books. The first treats fully of the important part played 

 by Bacteria in infection and contagion, showing, in fact, 

 that these organisms arc the causes and carriers of the 

 various forms of disease. In the second, after an exhaustive 

 account of the process of alcoholic fermentation has been 

 given, a new theory of it is propounded, based, not upon 

 chemical principles, like that of Liebig, but upon the 

 principles of molecular physics. Fermentation is defined 

 as being " the communication of the oscillations of the 

 molecules, groups of atoms, and atoms of the substances 

 composing the living protoplasm to the molecules of the 

 fermentible substance, in consequence of which the equi- 

 librium of the molecules of that substance is disturbed, 

 and decomposition is the result." It is also pointed out 

 that, in the case of yeast, the sugar is to some extent 

 decomposed within the cells, but for the most part outside 

 them. 



Though this account of his works is but little more 

 than an enumeration of them, yet it will suffice to show 

 how important are Nageli's contributions to botanical 

 science in the departments of morphology, anatomy, and 

 physiology, not merely as additions to the accumulated 



store of facts, but as new generalisations from those facts, 

 and as opening up fields for future research. 



Sydney H. Vines 



PROF. TAIT ON THE FORMULA OF 

 EVOLUTION^ 

 A N OTHER point to which I ought thus early to direct 

 -i*- your attention is the necessity for perfect definite- 

 ness of language in all truly scientific work. Want of 

 definiteness may arise from habitual laziness, but it much 

 more commonly indicates a desire to appear to know 

 where knowledge is not. Avoid absolutely all so-called 

 scientific writings in which (as Clerk-Maxwell said) the 

 attempt is made to "give largeness of meaning" to a 

 word by using it sometimes in one sense and sometimes 

 in another. It is true that we may thus economise in our 

 language, and avoid the necessity for introducing new and 

 hard terms. But it would be a most expensive and per- 

 nicious economy. It is only a blockhead who could 

 object to the use of a new term for a new idea. 



Our only source of information in physical science is 

 the evidence of our senses. To interpret truly this 

 evidence, which is always imperfect and often wholly 

 misleading, is one of the tasks set before Reason. It 

 is only by the aid of reason that we can distinguish 

 between what is physically objective, and what is merely 

 subjective. Outside us there is no such thing as noise or 

 brightness : — these no more exist in the aerial and 

 ethereal motions, which are their objective cause, than 

 does pain in the projectile which experience has taught us 

 to avoid. You will find many prominent ideas, relics of 

 a less enlightened age, from which Natural Philosophy 

 has not yet wholly shaken itself free, which owed their 

 existence solely to the confusion of the subjective with the 

 objective. 



With observation and experiment as our sole sources 

 of information we have no right, in physical science, to 

 introduce a priori reasoning. We may (unprofitably of 

 course) speculate on what things might have been, but 

 we must not dogmatise on what they ought to have been ; 

 we must simply try to discover what they are. 



For aught that we can tell, the properties of matter, 

 and physical laws in general, might have been other than 

 we find them to be. How can any one of us tell whether 

 his conscious self might not have been associated in life 

 with the body of an Eskimo or of a New Zealander, instead 

 of with what he (no doubt) considers its much preferable 

 tenement? Speculations of such a kind must always be 

 wholly unproductive and unprofitable, but for all that we 

 cannot but allow that they are not intrinsically absurd. 



Some years ago a critic of Mr. Herbert Spencer's 

 Philosophy happened to quote from a book of mine the 

 remark I have just made (that the properties of matter 

 might have been other than we find them to be). Mr. 

 Spencer's observation on this point is highly .instruc- 

 tive. Had he not been a severely grave philosopher I 

 should have taken it for a joke. He said, "Does this 

 express an experimentally ascertained truth ? If so, I 

 invite Prof. Tait to describe the experiments."' Mr. 

 Spencer has quite recently published a species of ana- 

 lytical inquiry 3 into my "mental peculiarities," "idiosyn- 

 crasies of thought," "habits of mind," "mental traits," 

 and what not. From his illustrative quotations it appears 

 that some or all of these are manifested wherever there 

 are differences between myself and my critic in the points 

 of view from which we regard the elements of science. 

 Hence they are not properly personal questions at all, but 



' Part of an Introductory Lecture delivered October 26, 1880. 



" Id my letter (Nature, vol. i.t. p. 402) will be found an illustrative 

 anecdite, which Mr. Spencer decl.ires to be •'not to the foini." A great 

 scientific nun, to whom I showed the correspondence, remarked that Mr. 

 Spencer must be the only man in England who could not see the perfect 

 appositeness of the anecdote. ,„,.„. , 



3 AfJ.cndix to First PrincipUs, dealing with Criticisms. (Williams and 

 Norgate, 1S80.) 



