1899] CONDITIONS OF GROWTH 467 



ideas, which opens new vistas, which suggests new experiments. To the neophyte 

 it opens quite a new train of thought ; it shows what ought to be done, what has 

 been done, and what could and should be done. For, most certainly, Mr. 

 Davenport's book is of the provisional and temporary sort : before ten years he 

 will have to begin it again, adding to each chapter, and opening new chapters, 

 if only we, his readers, do read him as we should, and take the hints which he 

 gives at each page. This "if," however, is a mere "oratory precaution"; there 

 is no doubt as to the future of experimental morphology ; the number of workers 

 in the field is steadily increasing. 



The matters considered by Mr. Davenport in this second part of his book are 

 all related to growth. Growth is an important subject-matter, practically as well 

 as from the speculative standpoint, and it is a very important matter that the 

 agencies which exert an influence on growth should be clearly recognised. The 

 agriculturist and breeder are as much interested in this as the physician and 

 biologist. 



The agencies referred to are numerous, for " that property which protoplasm 

 among all substances alone displays of increasing itself for an indefinite time 

 and to an indefinite amount " is much influenced by external conditions : by 

 chemical agents, by water, by the density of medium, by molar effects, by gravity, 

 by electricity, by light, in brief, by complex agents ; and each of these conditions 

 is the subject-matter of a chapter in Mr. Davenport's book. 



Generally speaking, of course, each chapter is a summary, an abstract of the 

 work which has been done by various workers, the author himself often included, 

 and a bibliographical list of references is the necessary complement of the text. 

 It must be said that no important paper seems to have escaped Mr. Davenport's 

 notice. However, in some cases, there are references which ought to be taken 

 account of. In the chapter where the author speaks of the chemicals and of 

 their distribution among organisms, no reference is made to Fliche and Gran- 

 deau's investigations concerning the chemical composition of various species of 

 plants nearly related to each other ; nor to recent investigations concerning the 

 presence of copper in pla.nts. Of course, some of the latter are too recent to 

 have been included in the book, as they have been published only two months 

 ago (in Botanical Gazette, by D. G. MacDougal) ; but others are of older date, 

 such as those of J. B. Skertchly and Lehman ; others are to be found in Schimper's 

 recent Pfianzen-Geogra'phie. 



Concerning the effect of flowing water upon the direction of growth, I 

 would also refer Mr. Davenport to a paper of Arnould Locard on the fauna of 

 the water-pipes in Paris ; the French malacologist observes that in the water- 

 pipes, where the flow is rapid, Dreissensia polymorpha, which is abundant, 

 relinquishes its curved form to become straight, and other mollusks — Lymnaea, 

 for instance — assume a specially elongated form under the same influence. 



And concerning the effect of light, and especially monochromatic light, some 

 interesting facts are to be found in Finsen's investigations. The latter have 

 been recently summarised and brought together in a pamphlet on Phototherapy. 

 It must not be inferred from the preceding lines that Mr. Davenport is not 

 well informed ; and while I refer him to the facts and papers mentioned, I only 

 wish to give what help and aid a reader should always give an author when he 

 meets with a carefully constructed work in which he takes a great interest. 

 This is co-operation, not criticism. 



A review of Mr. Davenport's book is hardly possible, in what space is avail- 

 able ; it is so very analytical that, of course, every biologist should read it for 

 himself, and make use of it for new experiments. There are any number of 

 points which require new and full investigation. For instance, the influence of 

 light. Retardation of growth is induced by light in most aerial plants, while 

 in animals acceleration obtains ; and in both cases the effect is due to the same 

 rays, the chemically active. This is the general fact : a full study of the matter 

 would certainly prove very profitable. 



