280 



KNOWLEDGE. 



[Decembee 1, 1894, 



practical application in the use of the microscope. These 

 will lead the student to an intelligent understanding of the 

 instrument he uses. The book is illustrated with forty 

 figures in the text and seventeen fine reproductions of 

 photo-micrographs. It is a work such as should be in the 

 hand of everyone who purchases a microscope for serious 

 study. There are several important treatises on various 

 branches of microscopy, and many little books of mediocre 

 quahty, but we know of no volume so suitable for the 

 self-taught student as the one before us. 



Lectures on the Darwinian Theory. Delivered by the late 

 Prof. A. Milnes Marshall, F.E.S. ; edited by C. F. Marshall, 

 M.D., B.Sc. Pp. 228. (London : David Nutt, 1894.) Of 

 the late Prof. Milnes Marshall it may be truthfully said, as 

 he himself said of Buti'on, "he led many to think about 

 and take an interest in natural history, and to add to it 

 by their own observations, who would not otherwise have 

 done 30." An original thinker, an eminent investigator, a 

 lucid writer, and an eloquent lecturer, he was an ideal 

 exponent of scientific truths. The series of lectures 

 recorded in this volume were delivered in connection with 

 the Extension Lectures of the Victoria University during 

 1893, and they really constitute the most entertaining 

 description of Darwinism that it is possible to obtain. 

 The work opens with a historical account of the theory of 

 evolution, and then in turn come artificial and natural 

 selection, the argument from palseoutology, the argument 

 from embryology, the colours of animals and of plants, 

 objections to the Darwinian theory, the origin of verte- 

 brated animals, and the life and work of Darwin. Prof. 

 Marshall had a thorough grasp of his subject, and he was 

 an earnest disciple of Darwin. If he had lived to see the 

 present volume through the press, some portions of it 

 would doubtless have been amplified and altered ; but even 

 as it stands it is a worthy monument to his brilliant 

 qualities, and an excellent statement of the development 

 of the theory of evolution. 



By Moorhiml and Sea. By Francis A. Knight. Pp. 21.3. 

 (London : Elliot Stock, 1898.) Gentle reader, you should 

 get this book. It is a book to read when light mental refresh- 

 ment is required ; a book to pick up when the dry bones of 

 science have begun to pall upon your appetite ; when you 

 have had enough instruction and want to be entertained. 

 The author is a keen and sympathetic observer of Nature — 

 a naturalist with poetic fancy like Gilbert White and 

 Bichard Jeiieries. There are now many writers on what 

 may be termed the poetry of science, but none ■mute more 

 agreeably than Mr. Knight, or express their thoughts in a 

 more attractive style. We have only one word of objection 

 to this collection of papers originally contributed by the 

 author to various journals ; it is, that the two or three 

 papers on subjects not connected with natural history 

 would have been better omitted. 



BOOKS EECEIVED. 



J Treatise on Chcmix/ry. Bt Sir H. E. Eoscoo, F.R.S.. and C. 

 Schorleinmer, F.R.S. Vol.' I., The Non-Metallic Elements. (Mac- 

 millan & Co.) 



A Lahoratori) Manual of Organic Cheynistri/. Bv AV. K. Orndorff. 

 (D. C. Heath & Co.) 



Fhysiologiffor Begitmrrs. By M. Foster, M.A., M.D., F.R.S. , and 

 Lewis E. Sliore, M.A., M.U. (Macmillan & Co.) 



Travels with a Hunbeam ; or lElemenIs of Aslrononxy. Parts land 

 2. By Artlnir Z. Dadi, (Bii-mingham ; W. Gr. Moore & Co.) 



JSv Vocal IVoods and Waters. By Edward Step. (Bliss, Sands & 

 Foster.) 



On Fedal and Antipedal Triangles ; lieing an at/emjtt to iueesti- 

 gate the Latcs of their Ecolntion. By A. S. GUosli, F.R.A.S. (Patrick 

 Press, Calcutta.) 



First Things First. By the Rev. a. Jackson, B.A. (Hodder & 

 Stoughton.) 



Life and Mind ; on the Sasis of Modern Medicine. Bv Robert 

 Lewins, M.D. (W. Stewart & Co.) 



The Vaccination Question. By Arthur Wollaston Huttou. 

 (llethueu & CV) 



Brief Notes on the Physical and Chemical Properties of Soils. 

 By R. "Warington, F.R.S. (Ch-apiuau & Hall.) 

 ' t<cienceforAll. Part 58. (Ca'sell & Co.) 



The Soiial Natural Mistori/. Edited bv Richard Lydekker, B A., 

 F.R.S. (\Vnrne & Co.) 



The Sei-ieu- of Seriews for November. (125, Fleet Street, E.C.) 



The Eighth Annual Seport of the Societe Astronomi'iue de France. 



The American Geologist. (The Geological Publishing Co., 

 Minneapolis), 



The Journal and Transactions of the Royal Photographic Society of 

 Great Britain. (W. Watson & Sons.) 



Catalogue of Slides, Optical Lanterns, 

 Apparatus. (E. G. Wood.} 



Catalogue of 3Iicroscopes and .ipparatus. 



Catalogue of Microscopes and Apparatus. 



and Dissolring Vietvs 



(R. G-. Mason.) 



(R. & J. Beck, Ltd.) 



THE INDUSTRY OF INSECTS IN RELATION 

 TO FLOWERS. 



By the Rev. Alex. S. Wilson, M.A., B.Sc. 



AS fertilizing agents, insects perform an indispensable 

 service to flowers ; it is only a small proportion 

 of the available species, however, that are utilized 

 for this work. Many blossoms depend for their 

 fertilization exclusively on a single order of insects ; 

 others avail themselves of only a few families, and in some 

 instances a flower's visitors appear to be confined almost 

 entirely to a single species of insect. Besides attractions 

 such as honey, scent, and brilliant colours, most flowers 

 exhibit contrivances for the exclusion of undesirable guests. 

 And it is not simply creeping and gnawing kinds, whose 

 visits are positively injurious, that are thus excluded ; 

 many winged and harmless species are also denied access. 

 The size and shape of an insect may even be well adapted 

 for the fertilization of a particular flower, and yet its visits 

 may be discouraged. Since the chances of cross-fertiliza- 

 tion increase with the number of visitors, it is clearly of 

 advantage for flowers to be visited by the utmost possible 

 variety of insects ; any limitation might, therefore, be 

 regarded as prejudicial. The disadvantage of restriction 

 may indeed be more than coimterbalanced, as Herman 

 Miiller points out, if thereby the attractiveness of the 

 flowers for special insects be increased, but the benefit 

 arising from the limitation of insect-visits perhaps admits 

 of fuller elucidation than it has yet received. The exclusion 

 of certain insects from a particular flower, we have been 

 accustomed to ascribe to the fact of their size and shape 

 being ill-adapted for its fertilization ; but there are other 

 reasons, and it is to these that we wish to direct attention 

 in this paper. 



To appreciate the significance of the restriction, it is only 

 necessary to compare the relative importance of the number 

 of visitors which a flower receives with the industry of the 

 individual visitors. If all insects of suitable size and shape 

 visiting flowers were equally industrious, then restriction 

 would be disadvantageous. The fundamental reason for a 

 limited selection is to be found in the circumstance that 

 the efficiency of any set of fertilizing agents depends not 

 so much upon their numbers as upon the number of 

 separate flowers which each individual visits, or, in other 

 words, upon their industry. Ten visits made by ten 

 difl'erent individuals are far less effectual than the same 

 number of visits performed by a single insect. A small 

 number of bees, butterflies, or other systematic visitors 

 will fertilize far more flowers than a much larger number 



