42 ENTOMOLOGICAL NEWS. [Jan., 'l6 



phasize in a journal devoted rather to pure than to applied entomology. 



Biitschli (1870), Kowalevski (1871), Grassi (1884), Blochmann (1889), 

 Petrunkewitsch (1901, 1903), Dickel (1903) and Xachtsheim (1913) 

 have described various phases of the development of the egg of the 

 honey bee, but Nelson's work is more extensive and thorough-going 

 than any of these, although it is devoted to the embryonic history of 

 the workers and queens only, not of the drones. 



The first chapter (3 pp.) gives an historical review of the embry- 

 ology of the honey bee, the second (pp. 4-15) describes oviposition 

 and the organization of the undeveloped egg. Chapters III-VII (pp. 

 16-112) treat of the development of the embryo as a whole from 

 cleavage, through the formation of blastoderm and germ layers to 

 acquirement of the external form of the larva. Chapters VIII-XIV 

 (pp. 113-245) deal with the development of organ-systems, especially 

 the nervous system (Chap. VIII, pp. 1 13-166), and the fate of the 

 yolk and yolk cells. 



Special efforts were made to determine the rate of development and 

 as a result the seventy-six hours spent within the egg are divided into 

 fifteen stages, designated by the numerals I-XV, whose several lengths 

 extend from 2 to 22 hours. These are discussed (in Chapter XV), 

 tabulated (p. 247) and illustrated on the plates which represent views 

 of entire eggs fixed, stained and mounted in balsam. (Certain dif- 

 ferences in the ages of these stages will be observed on comparing 

 page 247 with pages 99-105). 



The sixteenth chapter comprises a description of the technique 

 emplojed and an excellent summary of the entire course of develop- 

 ment (pp. 253-261). A list of abbreviations applying to all the figures, 

 a bibliography on insect embryology (pp. 265-272) and an index (pp. 

 273-282) complete the text. 



The book appears to us to be very clearly written and the figures 

 excellent. A.lthough there are nom.inally ninety-five text figures, their 

 actual number is much greater, as many of them are two-, three-, or 

 even five-fold. Dr. Nelson does not confine himself to his own careful 

 study of embryos, but compares his findings with those of previous 

 investigators of the embryonic development of the honey bee, of other 

 Hymenoptera and of insects in general. These features will render 

 his book of great use to all laboratories where any phase of insect 

 embryology is touched on, however lightly. 



Turning to a few of the special or novel features of this volume, 

 we may note the useful summary of the conclusions of embryologists 

 as to the origin of the mesenteron of insects (pp. 71-77)- Dr. Nelson 

 thinks that the relation of the mesenteron rudiments in the honey 

 bee may be interpreted in either of two ways: they may be referred 

 to the mesoderm, or considered as purely blastodermal in origin. 



