36 



THE EMBRYOLOGY OF THE HONEY BEE 



:.s o" 



i/\/-; 





© 



Fig. 15. Transverse section through the anterior region of an egg 

 about 17-20 hours old, showing the nuclei of the blastoderm arranged in 

 two layers, x 243. 



by the fact that very many of the cells situated next to the peri- 

 pheral surface are pyriform in outline, with their slender ends 

 reaching inwards to the basement membrane. These alternate 

 more or less regularly with shorter cells lying close to the base- 

 ment membrane, but which frequently possess a slender peri- 

 pheral process. This apparent two layered condition was 

 described and figured by Kowalevski (1871), who explained it 

 ingeniously by supposing it to be an artifact, brought about dur- 

 ing the formation of the action of the fixing agent. The latter 

 was assumed to have contracted the layer of cells first appearing 

 at the surface of the egg, closing up the intervals between them 

 and crowding them down on those cells arriving later. This 

 same stage has also been figured for the drone egg by Petrunke- 

 witsch (1901, Fig. 24), a dividing cell is also shown. Oblique 

 divisions of the blastoderm cells are also described for Polistes 

 by Marshall and Dernhehl (1905). 



Viewing the blastoderm as a whole, it appears more compact 

 and sharply outlined than it was directly after its inception ; it 

 now constitutes a well developed epithelium. Both its outer and 



