NA TURE 



[May 6, 1897 



Sestini, Valente, Fabris and Andreocci, the chemistry of 

 santonin. At the same time that he was called to Rome 

 he was made a Senator of the kingdom, and as a 

 moderate Liberal he has taken his share in the 

 consolidation of the constitution of regenerated Italy. 



Cannizzaro, when compared with such men as Berthelot 

 and certain of the leaders of the German schools of 

 chemistry, or even with some of the younger generation 

 of Italian chemists, cannot be called a voluminous 

 writer. In all about eighty memoirs have proceeded 

 from his laboratory. It is on the special quality and 

 character of his published work, rather than on its extent, 

 or on the range and variety of its subject-matter, that his 

 fame depends. In this respect he resembles the late 

 August Kekule. The names of both men will for ever be 

 associated in the history of chemistry with the promul- 

 gation of generalisations which mark epochs in the 

 development of chemical science. Cannizzaro's great 

 merit consisted in being the first to clearly point out the 

 bearing on chemical theory of the hypothesis which is 

 commonly associated with the name of his countryman 

 Avogadro, but which Cannizzaro himself, in his well-known 

 lecture delivered before the Fellows of the Chemical 

 Society in 1872, associated also with the names of 

 Ampere, Kronig and Clausius. This, perhaps, is not 

 the time and the place to discuss the question of 

 whatever claims John Dalton may have to be the 

 first to recognise the fundamental truth embodied 

 in the statement that gases, under comparable con- 

 ditions, contain in equal volumes equal numbers of 

 molecules, whatever may be their nature and their 

 weight. For the moment we are concerned only with 

 the fact that it remained to Cannizzaro to show that 

 the hypothesis afiforded the means of placing the most 

 important of all chemical constants — the atomic weights 

 of the elements — on a definable and intelligible basis, 

 and thereby of rendering our conceptions of atoms and 

 molecules, atomic weight and molecular weight, of 

 gaseous volumes and valency, and of all that is associated 

 with or follows from these conceptions, more logical, con- 

 sistent, and harmonious. What Cannizzaro did, in a word, 

 was to throw light upon what was obscure, to introduce 

 order where all was confused and contradictory. Hence 

 his " Summary of a Course of Chemical Philosophy," 

 published in 1858, will occupy in the history of chemical 

 doctrine a position as a classic, not less honourable than 

 Dalton's ever memorable " New System." There were, 

 of course, difficulties to be overcome, and inconsistencies 

 to be reconciled : certain facts, indeed, appeared to be 

 hopelessly opposed to the hypothesis which Cannizzaro 

 sought to make the corner-stone of the edifice of modern 

 chemistry. But these difficulties have been gradually 

 swept away, and the very facts which at first seemed 

 incapable of being brought into line, are now seen to 

 afford the strongest support to the truth and universality 

 of the theory. 



The theory of Avogadro, indeed, has been approached 

 from independent, although converging standpoints, and 

 its position is now secured by the concurrence of inde- 

 pendent testimony. Mathematical conceptions of the 

 nature of gases have shown its necessity. Chemical 

 facts, for a time, were seemingly opposed to it, and hence 

 it was neglected and ultimately forgotten by chemists. 

 NO. 1436, VOL. 56] 



They were, however, being driven back to it in spite of 

 themselves ; and it in no sense detracts from his merit to 

 affirm that even if Cannizzaro had not perceived the truth, 

 the rapidly accumulating mass of evidence would have 

 forced others to recognise it. Indeed the substantial 

 unanimity with which Cannizzaro's doctrine was received, 

 immediately that it became generally known, is a proof 

 that the time was ready for it. It is not too much to 

 say that its effect on the minds of chemical thinkers was 

 as profound as that described by Cannizzaro himself in 

 the memorable lecture before alluded to, when he re- 

 minded us of Thomas Thomson's account of the 

 impression produced upon him by Dalton's own verbal 

 explanation of the atomic theory. To paraphrase his 

 words: they were enchanted with the new light which 

 burst upon their minds, and saw at a glance the immense 

 importance of such a theory. 



Hence then, when Cannizzaro visited this country inr 

 1872, to deliver the Faraday Lecture to the Fellows of 

 the Chemical Society, of which he has been a Foreign 

 Member since 1862, he spoke to willing and receptive 

 ears, and to a body of men to whom his doctrine was 

 already an established article of their chemical creed. 



Cannizzaro is a Foreign Member of many learned 

 Societies ; nearly every Academy in Europe, indeed, has 

 delighted to honour him. In 1889 he was elected a 

 Foreign Member of our Royal Society, and two years 

 later he was awarded the Copley Medal for his services 

 to chemical theory. May he long be spared to wear the 

 many honours he has so worthily earned, and to enjoy, in 

 health and increasing prosperity, the respect and esteem 

 of a multitude of friends in both hemispheres ! 



T. E. Thorpe. 



EXPERIMENTAL RESEARCHES ON THE 

 PHYSIOLOGY OF REPRODUCTION. 

 Die Bedingun^en der Fortpflanztcng bet einigen Algen u. 

 Pihen. Von Dr. Georg Klebs, Professor in Basel. 

 Mit 3 Tafeln u. 15 Text-figuren. (Jena: Gustav 

 Fischer, 1896.) 



IT has long been recognised that in the life cycle of a 

 large number of plants and also of some animals 

 two very distinct modes of reproduction, the sexual and 

 the asexual, recur in a rhythmical fashion. 



This fact, crystallised by Steenstrup in his famous 

 doctrine of alternation of generations, has ranked as one 

 of cardinal importance in the treatment of the higher 

 groups of plants ever since Hofmeister showed that the 

 sequence of events in their several life-histories was 

 essentially identical with that obtaining in a moss or 

 in a fern. True it is that in respect of algae and fungi 

 there existed an uncomfortable arricre pensee that all 

 was not quite right, and indeed certaih facts seem to be 

 definitely opposed to the general extension of the doctrine 

 to the various members of these classes. Curiously enough 

 it seems not at once to have been clearly apprehended that 

 one has hardly any right to expect to find alternatiorv 

 recurring regularly in these primitive forms ; for the very 

 characters which we regard as indicative of primitiveness 

 consist exactly in those negative conditions implied 

 in an, as yet, undeveloped state of division of labour. 

 But it is obvious that, before alternation could possibly 

 have become part of the regular physiological (and 



