34 



NATURE 



[September io, 19 14 



reservoir sites and the use of the microscope and 

 photomicrography. The latter portion of the book, 

 containing descriptions of various groups of 

 water-cJrganisms, has also been revised, and the 

 plates showing the commoner organisms of water 

 have been printed in colours, making identification 

 easier. 



The book is one which should find a place in 

 every bacteriological and public health laboratory 

 and in the office of the water-engineer. 



R. T. Hewlett. 



LETTERS TO THE EDITOR. 

 [The Editor does not hold himself responsible for 

 opinions expressed by his correspondents. Neither 

 can he undertake to return, or to correspond with 

 the writers of, rejected manuscripts intended for 

 this or any other part of Nature. No notice is 

 taken of anonymous communications.} 



Micromillimetres and Micromicrons. 



It is very desirable that men of science should 

 adhere to the conventions which have been established 

 with regard to the use of the terms employed for units 

 in the metric system. It has been generally agreed 

 that the prefixes mega- and micro- should indicate the 

 multiplication and division respectively by a million of 

 the unit expressed by the term they precede. In this 

 way a micrometre usually shortened to micron, means 

 a millionth part of a metre, or, in other words, a 

 thousandth of a millimetre ; and a microtnillimetre 

 signifies a millionth part of a millimetre, or, what is 

 the same thing, a thousandth part of a micron. It is, 

 therefore, to be regretted that in the translation, pub- 

 lished in Geneva, by L. Duparc and Vera de Dervies, 

 of Nikitin's excellent account of Fedorov's "universal " 

 method of microscopical mineral research we find the 

 term micromicron employed in place of micromilli^^ 

 metre. The former term should mean a millionth 

 part of a micron — that is to say, a metre xio-'-, a 

 unit that might be usefully employed in expressing 

 intermolecular or interatomic distances in crystals, 

 which we are now at last in a position to determine 

 in many cases. John W. Evans. 



Imperial College of Science, South Kensington, 

 September 3. 



Origin of Species. 



In Darwin's great work on this subject he claims 

 that Dean Herbert, in 1822 and 1837, held that "single 

 species of each genus were created in an originally 

 highly plastic condition, and that these have produced, 

 chiefly by intercrossing, but likewise by variation, all 

 our existing species." 



Years of study along this line have assured me that 

 he was right. I am now especially interested as I 

 have a few trees on hand which seem to prove this 

 position. They are a cross between Quercus and 

 Juglans, which bears walnut-like nuts on a tree which 

 bears oak-like leaves : at least a new species and per- 

 haps a new genus. If this tree had been found in the 

 forest it would have caused no remarks, but originat- 

 ing in the garden it has become the wonder of the 

 world. Here is an oak tree in appearance which 

 bears perfect walnuts, all originated in one year and 

 fairly productive and fixed. 



This tree gives me further evidence of the fact 

 that all sexual life known to us, both animal and 

 vegetable, has sprung from hybrids. 



Newton B. Pierce. 



Pacific Coast Laboratory and Wild Plant Improve- 

 ment Gardens, Santa Ana, California. 



NO. 2341, VOL. 94] 



LECTURES ON THE ANIMAL KINGDOM 

 BY LINN^US.^ 



IT is probable that most modern zoologists, 

 when unfamiliar with the Scandinavian 

 tongues, know little of the zoological writings of 

 Linnaeus beyond the "Systema Naturae," and 

 that from this restricted evidence they draw the 

 natural but entirely erroneous conclusion that, 

 considered as a zoologist, Linnaeus was little more 

 than a methodical compiler, classifier, and name- 

 giver. If, moreover, the modern zoologist is not 

 so well acquainted with the history of his science 

 as he should be, he is apt to seize rather on the 

 defects, or even absurdities, in the " Systema " 

 as compared with his own knowledge, and to 

 ignore the real advances made by the great Swede 

 over the attempts of his predecessors. There are, 

 as we have hinted, many writings by Linnaeus that 

 prove the falsity of such opinions, and now an- 

 other has just been issued by the University of 

 Uppsala which enables one to read between the 

 lines of the "Systema," and to realise the wide 

 zoological knowledge and still more the philo- 

 sophy and humanity on which it is based. The 

 volume consists of a complete course of lectures 

 on the animal kingdom, delivered by Linnaeus 

 between 1748 and 1752, and collected from the 

 notes made by various pupils, of which more than 

 forty manuscripts are preserved in the university 

 library. The collation of these manuscripts was 

 begun by the late Dr. M. B. Swederus, and has 

 been completed by Dr. Einar Lonnberg, with the 

 help of Miss Greta Ekelof. The lectures are 

 followed by a detailed commentary and by short 

 accounts of 123 authors quoted by Linnaeus; these 

 two parts are by Dr. Lonnberg, who has availed 

 himself of the help of various colleagues, living 

 and dead. 



And now of Linnaeus as a lecturer, what may 

 we think? Approaching him at second-hand, and 

 without the magic of his enthusiastic presence, 

 we yet see how he infused a living and practical 

 interest into what might so easily have been a 

 dry catalogue of species. An undergraduate's 

 notebook omits much that the writer does not con- 

 sider essential, the humorous asides, the occa- 

 sional divagations, the purple patches ; but the 

 students of Uppsala realised that they listened to 

 no ordinary man, and it is clear that much has 

 been taken down verbatim. Certainly, that must 

 be the case with the stately Prolegomena, which- 

 we should like to have translated in full, but must 

 at least make some attempt to abstract : — 



Generation after generation of earthly creatures 

 comes into being only to pass into nothingness. 

 And yet, though fashioned only for vanity, each 

 creature struggles to preserve its life; one preys 

 upon another so that nature is a helium omnkirn 

 perpetuum in omnes, and of all creatures man is 

 most inhuman. And yet man, with his works of 

 wisdom, his castles and towers, comes only to 

 dust. What is the object of so vain a contriv- 

 ance? The answer is given by natural history. 



1 Linn^s Forelasningar ofver Djurriket, md understod af Svenska Staten 

 for Uppsala Universitet utgifna och forsedda med forklarande anmarkningar 

 af Einar Lonnberg. (Uppsala, 191 3.) 



