168 SCIENCE PROGRESS 



The chapter on practical microscopy of metals contains all the necessary 

 information a beginner would require in order to polish samples of metal and 

 develop their structure. It also includes much useful information in connection 

 with the apparatus and the various methods employed for obtaining records of 

 the results photographically. 



The section dealing with the special metallography of iron and its alloys differs 

 from the original German, as it has been re-written and brought thoroughly up to 

 date by the translator. This portion of the work deals with the equilibrium curve 

 and the microstructures of the iron carbon series of alloys in a very able manner. 

 Not only are the " slowly cooled" structures illustrated, but the effects of varying 

 heat treatment are also fully described. 



Both the author and translator are to be congratulated on the production of 

 this work, and we can most confidently recommend it to all who are interested in 

 the science of metallography. 



W. H. Merrett. 



Entomology, with special reference to its Biological and Economic 

 aspects. By Justus Watson Folsom, Sc.D. (Harvard). (London : 

 Rebman, 1906 ; price 14s.) 



This work on Entomology is quite original in its treatment, and will be of great 

 value when placed with such works as Berlese's Gli Insetti, and Sharpe's Insects 

 in the Cambridge Natural History Series, for we shall then have a wide field 

 of reference on this subject in its various branches. 



The author divides the work up into thirteen chapters and an appendix dealing 

 with Literature. The subjects of these chapters are as follows : Classification, 

 Anatomy and Physiology, Development, Adaptations of Aquatic Insects, Colour 

 and Coloration, Adaptive Coloration, Origin of Adaptations and of Species, 

 Insects in relation to Plants, Insects in Relation to other Animals, Interrelations 

 of Insects, Insect Behaviour, Distribution, and Insects in Relation to Man. 



Many of these subjects will at once strike us as being of great interest. The 

 chapter on Classification is brief, and might almost have been left out. The author 

 treats insects under no less than seventeen different orders, which is to be 

 regretted. There is no valid reason for placing the Fleas in a separate order, 

 Siphonaptera ; they are Diptera. It is surely unnecessary to place the neurop- 

 terous Panorpidae as a distinct order, Mecoptera. The Termites he places 

 in another order, Platyptera, and the Aptera are divided into two orders, 

 Thysanura and Collembola. The chapters on Anatomy and Physiology are well 

 worked out, and are interestingly written. 



The subject of Colour and Coloration is treated very fully ; the diffraction 

 of light by fine close parallel striae is shown to produce the brilliant iridescent 

 hues of many butterfly scales. A species of the gorgeous genus Morphio is 

 stated to have no less than 1,400 striae on its iridescent pigmented scales per 

 millimetre, and further the author explains that the interference colours of 

 butterfly scales may be due also to the lamination of the scale and to the over- 

 lapping of two or more scales. Pigmental colours and their nature are also 

 entered into. Seasonal and sexual coloration are dealt with, but not to the extent 

 that they might have been. Much interesting reading is found in the chapter 

 dealing with Insects in Relation to Plants. Notable amongst the information 

 given here is that upon the "ant-plants." Belt found in Nicaragua species 

 of Acacia with large hollow stipular thorns inhabited by ants of the genus 



