236 JOURNAL OF THE EOYAL HORTICULTURAL SOCIETY. 



For the clear and plain way in which this complex history is given in a 

 few pages one can hardly be too grateful. Dr. Scott shows that 

 morphological characters are sometimes adaptive, and questions the 

 theory of mutations, " the last resort of the phylogenetically destitute." 



" The Influence of Environment on the Forms of Plants," by 

 Professor Klebs (Heidelberg). For Sempervivum he finds that with 

 strong light and vigorous carbon-assimilation a considerable increase in 

 the supply of water and nutritive salts produces active vegetative growth, 

 but a decrease in water and salts results in active flower-production. 

 " Every experimental investigation shows that the fluctuation of characters 

 depends on fluctuation in the external factors." " Abnormal developments 

 of all kinds in stems, leaves, and flowers may be produced by parasitic 

 insects, fungi, or by injury." These few extracts will serve to show the 

 value of this important contribution for all practical horticulturists. 



" Experimental study of the Influence of Environment in Animals," 

 by Professor Loeb (California). The author gives his curious experiments 

 in hybridizing sea-urchins with molluscs, &c. There is also much 

 concerning the effect of light, gravitation, and temperature, especially on 

 Copepoda, butterflies, and sea-urchins. He considers that every species 

 has its own specific nuclear material or nuclein. 



" The Value of Colour in the Struggle for Life," by Professor E. B. 

 Poulton, describes in detail every kind and form of mimicry. Most 

 of his instances are taken from butterflies or other insects. 



" Geographical Distribution of Plants," by Sir William Thistleton 

 Dyer. Darwin's original views are very thoroughly discussed and con- 

 trasted with those of Bentham, Hooker, and Wallace. There are also 

 many interesting quotations from Guppy's recent work and some remarks 

 on the influence of the Glacial period on the European Flora. 



" Geographical Distribution of Animals." Dr. Hans Gadow shows 

 that this is nothing less than the history of the evolution of life in space 

 and time. He attempts to reconstruct the geography of the successive 

 geological epochs and deals with such difficult questions as convergent 

 species, adaptation, &c. 



"Darwin and Geology," by Dr. T. W. Judd. This article is almost 

 entirely an appreciation of Darwin considered as a geologist. 



" Darwin's Work on the Movement of Plants." Dr. Francis Darwin, 

 in this brief but interesting and important essay, describes the statolith 

 theory of geotropy, sleep movements, circumnutation, and other physio- 

 logical phenomena in the light thrown by recent researches. 



"The Biology of Flowers," by Professor Goebel, is concerned chiefly 

 with self- as contrasted with cross-fertilization, with cleistcgamy and 

 heterostyly. It is also for the most part a study and appreciation of 

 Darwin's work. 



"Mental Factors in Evolution." Dr. Lloyd Morgan's contribution is 

 psychological. " The history of man's higher progress has been mainly 

 the history of man's higher educability, the products of which he has 

 projected on to his environment. This educability remains on the 

 average what it was a dozen generations ago ; but the thought-woven 

 tapestry of his surroundings is refashioned and improved by each succeed- 

 ing generation." 



