108 THE CANADIAN ENTOMOLOGIST. 



ul ihe developniciU of the embryo the development of the wirious 

 organs is described: The nervous and tracheal systems, the oeno- 

 cytes, muscles, fat-body, circulatory and genital systems and ali- 

 mentary canal. A useful summary is given at the end of thel)Ook; 

 ill this connection we think tlie \ alue of tlii' book would lia\e been 

 enhanced b\' the inclusion of a summarx ;it the conclusion of each 

 chapter. 



On the Avhole, l)r. Nelson conlirms the obser\ations of the 

 pre\ious in\estigators who have studied the de\'eloi)ment of the 

 bee egg, and his work does not afford any striking differences or 

 discoveries. The account of the clea\age of the egg agrees in the 

 essential details with the earlier work. In regard to the \ exed 

 question of the origin of the mesenteron. the importance of which 

 has always been emphasised on account of its bearing of the broad 

 theor>- of the germ layers, the results of this study are held to lend 

 little support to the \iews of those who regard the mesenteron of 

 insects as arising from the ectoderm of the stomockeum or procto- 

 da^um, and to harmoni/e still less with the theor\- of the origin of 

 the mesenteron from cells remaining in the \()lk. The author 

 considers a hnal decision between these two ri\al interpretations 

 premature Certainly the honey bee is loo highly a specialized 

 member of a specialized order upon which to l)ase generalizations. 

 It is found that the anterior and posterior mesenteron rudiments 

 are formed from the blastoderm of the \entral plate by an inward 

 mox^ement of its cells. The book is characterized b>' a desire on 

 the part of the author to review the conclusions of prc\ious in- 

 vestigators of the embr\-olog>- of the hone>' bee and of other insects, 

 to present the results of his own study and tb leave the detailed 

 fliscussions of ri\al interpretations to those who j^rcfer the atmos- 

 phere of debate, and in a work of this character and puipose we 

 think such an attitude is perhaps desirable. 



The numerous excellent illustrations, on which the author is 

 to be heartily congratulated, increase the value of a book which 

 will be very useful to students of insect embryology, and to those 

 beekeepers who may be qualified by their training or mental 

 courage to appreciate what is undoubtedly the best account we 

 have of the development of the egg of the honey bee. 



C. Gordon Hewitt. 



Mailed March 14, 191 (>. 



