292 



REVIEW 



Dr J. A. NELSON. The Embryology of the Honey-Bee. (Princeton 

 University Press, London; Oxford University Press, 1915.) 

 Pp. 282. Price 8s. 6d. 



In this little book, although the author is " Expert in Bee-Culture 

 Investigations" in the Department of Agriculture, Washington, we find 

 no reference whatever to any of the problems suggested by bee-culture : 

 we have only an account of the early stages in the development of the 

 bee up till the time that it emerges as a grub from the egg-shell and 

 takes up its existence within a cell of the honeycomb. To the student 

 of comparative embryology however as distinguished from the economic 

 zoologist the book is welcome, for it gives a most painstaking and 

 thorough account of the formation of the blastoderm in the egg, of the 

 differentiation of ectoderm, endoderm, and mesoderm, and of the manner 

 in which these three layers are transformed into the most important 

 organs of the grub. About the formation of these layers in insects 

 there had developed a good deal of controversy. Heymons had main- 

 tained that in the higher insects, the endoderm, after giving rise to 

 cells which assisted in liquefying the yolk, disappeared, and that the 

 midgut was lined by ectodermal cells which grew in from the mouth 

 and anus. Now this view, which would upset all our ideas as to the 

 fundamental functional distinctions between the germ-layers, was 

 opposed by Hirschler who maintained that Heymons had been misled 

 by gaps in the series of stages which he examined, and that the endoderm 

 in the higher insects as in the lower forms the epithelium of the midgut. 

 In the volume before us Dr Nelson gives convincing proof that Hirschler 

 is right at least so far as the honey-bee is concerned. The book is 

 admirably illustrated: a number of plates illustrating whole mounts 

 are collected at the end, whilst interspersed with the text are a number 

 of figures illustrating the development of particular organs. The 

 technique employed is carefully explained and there are a number of 

 valuable hints on the effects of different kinds of preserving fluids. 

 The book will constitute a welcome addition to t he library of the scientific 

 zoologist. 



E. W. M. 



