8 



.VA TURE 



[November i, 1894 



of Bruges u'. 1600), and although they must have been 

 employed by scientific engineers, such as Brunei, the 

 subject of Graphical Statics as known to the mathe- 

 matician dates only from Maxwell's writings on the sub- 

 ject, and to Culmann's elaborate treatise in Crerman ; 

 also to Colonel Sir George Clarke's exhaustive work. 



The subject of Statics, which had come to a standstill, 

 was revivified by the graphical methods now employed 

 by every engineer and architect. 



But as the subject is nothing unless employed prac- 

 tically by the draughtsman on the drawing board, it has 

 not yet conquered the prejudices of the abstract mathe- 

 matician, although many problems of allied descriptive 

 geometry, required in the construction of inertia ellipses 

 and curves Tart iii. , are well worthy of the attention 

 of the pure geometer. 



The present treatise is designed as an elementary text- 

 book for the use of students of engineering ; and the 

 illustrations are drawn carefully to scale, representing 

 each some real object. 



The method of lettering, attributed to Bow, is now 

 more appropriately assigned to Henrici ; the author very 

 rightlv insists upon the fundamental importance of this 

 lettering, in emphasising the reciprocity existing in the 

 diagrams. 



Incidentally the method of Graphical Statics empha- 

 sises the proper treatment of Statical problems, which is 

 always to consider a "System of balancing forces; and 

 thus to banish the word Resultant from Statics unless 

 employed to represent the force which if reversed will 

 balance the remaining forces of the system. G. 



A Naturalist on the Prowl. By Eha. Pp. 257. 



(London : W. Thacker and Co., i S94.) 

 From Spring to Fall. By " A Son of the Marshes." 



Edited by J. A. Owen. Pp. 239. (London : William 



Blackwood and Sons, 1894.) 

 Thf. author of " A Naturalist on the Prowl " knows how 

 to write pleasantly on the natural history of the Indian 

 jungle. There is not a dull page in his book. It is only 

 rarely that we meet with a volume so full of interesting 

 observations, and so free from stodginess. In " Eha's " 

 company we travelled from the first to the last page, here 

 admiring the keenness of his perception, there laughing 

 at his humorous comments, and always made happy by 

 his geniality. He does not "prowl " to kill, neither is he 

 imbued with the spirit that induces many people to 

 collect shells and postage-stamps as specimens ; for 

 though he recognises that " without a collection, a man's 

 knowledge of natural history becomes nebulous, and his 

 pursuit of it dilettante," he also knows that there is a pos- 

 sibility of a man degenerating into a mere collector, and 

 ceasing to be a naturalist. Mr. R. A. Sterndale enriches 

 the volume with eighty illustrations, mostly sketched 

 from life. 



The works of " A Son of the Marshes," on country life 

 and scenery, are renowned for their simple beauty and 

 sympathetic expression. Under the editorship of Mrs. 

 Owen, the volume before us, like other books by the same 

 author, is delightful reading. 



Edible and Poisonous Mushrooms. By Ur. M. C. Cooke. 

 (London: S.P.C.K., 1894) 



It may be safely asserted that fewer kinds of fungi are 

 used for food in Great Britain than in any other country 

 in Europe. This is the more remarkable when we take 

 into consideration the indebtedness of the present ad- 

 vanced state of Mycology to the researches of our 

 countrymen, amongst whom may be mentioned Bolton, 

 Sowerby, Badham, Berkeley, and Broome. The author 

 of the work under consideration has also contributed 

 very materially to a knowledge of edible kinds of fungi 

 by various publications, and more especially in promoting 

 annual fungus forays in various parts of the country. 



NO 1305. VOL. 51] 



Poisonous fungi liable to be confounded with the 

 numerous edible kinds are very few in number, and the 

 majority of casualties, both at home and abroad, are 

 caused by eating Amanita phalloides, a fungus very 

 different in appearance from the common mushroom 

 {Agaricus c-ampi-stris), but which, probably from its neat 

 and attractive appearance and size, appears to commend 

 itself to unsuspecting persons, and being usually very 

 abundant and widely distributed, is likely to be a con- 

 tinual source of danger until its characters and general 

 appearance are more generally known. 



Dr. Cooke very properly condemns the various rule-of- 

 thumb methods for discriminating between edible and 

 poisonous kinds of fungi, and shows that the essential 

 characters of the various kinds must be thoroughly 

 grasped, as being the only certain means of identification ; 

 and this method, with Dr. Cooke's book as a guide, should 

 not prove a difficult task. The written descriptions of the 

 various kinds, without being technical, are very clear 

 and to the point, and the eighteen coloured plates are 

 excellent. Finally, the best methods of cooking are 

 given. The book is well printed, attractive externnlly, 

 and very cheap. 



LETTERS TO THE EDITOR. 



[The Editor does not hold himselj responsible for opinions ex- 

 tressed by his correspondents. Neither can he underlaki 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part o/'Naturb. 

 No notice is taken of anonymous communications. ] 



What are Acquired Characters? 



For some while past, as we all know, a great contest has been 

 raging as to whether acquired characters of an organism can or 

 cannot be transmitted from one generation to another ; and 

 mighty authorities, on the one side, say that they can be ; and 

 great authorities, on the other, aver that they cannot be. 



As a spectator of this contest, I have tried to understand it ; 

 and, in the first place, I have endeavoured to make out what is 

 meant by the uhrase " acquired characters'' ; or, in short, what 

 is meant by the word "acquired," as used, in this connection, 

 by Weismann, his friends, and his antagonists. 



It is evident that the word is not used in its primary and 

 natural signification • for, .is on the theory of evolution (on which 

 hypothesis the whole discussion proceeds), man has been 

 evolved from an anncba or an ascidian, or some other early 

 form, it follows that every character by which a man differs 

 from this, his firsl progenitor has been acquired at some time 

 between the two termini of the course of evolution, and, if the 

 word were used in its ordinary sense, it would further follow 

 that none of these characters could be transmitted by man to 

 his offspring. This is manifestly untrue, for the issue of a 

 woman is not simply an amuba. In fact, Weismann himself 

 implies plainly that he does not use the word " acquired " in its 

 ordinary signification, and asserts that its scientific value lies in 

 its restricted use. (" Essays on Heredity," English translation, 

 vol. i., first edition, p. 412.) 



It becomes then very important to get at an accurate and 

 workable definition of the word "acquired" for the purpose in 

 hand; and such a definition must, I conceive, satisfy the follow- 

 ing conditions : — (l) It must be such as to include all characters 

 that are "acquired " wiihin the restricteil meaning of the word, 

 and to exclude all characters that are not within the meaning ; 



(2) it must be staled in physical, and not in metaphysical terms ; 



(3) it must not be stated in terms derived from beredit.iliility 

 or the contrary, or in terms of any hypothesis or theory ; (4) 

 in order that it may be of use for scientific purposes, it must be 

 stated in terms that admit of ascertainment and verification. 



Of the imporlancc of a clear definition of these words every 

 one must, I think, be conscious ; and if authority were required, 

 wc have that of Prof. Weismann himself. " I should wish to 

 jioint out," hcs.ays, "that we ought above all to be clear as to 

 what we really mean by the expression 'acquired character.'" 

 (" ICssays," vol. i. p. 169.) 



Now, I do not profess to have read all that has come from the 

 pen of I'rof Weismann, and still less the whole literature that 



