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TEXT-BOOK OF ENTOMOLOGY 



The result of these and of later observations, especially those of 

 Blochmann on Musca, and those of Heider on Hydrophilus, show 



that the division-nuclei lie near 

 the centre of the egg, along the 

 longitudinal axis (Fig. 507, A). 

 Each of these nuclei is enveloped 

 by a star-shaped mass of proto- 

 plasm, and on the whole resem- 

 bles a wandering amoeboid cell. 

 These isolated masses of proto- 

 plasm are all connected by a fine 

 network of rays, which unite to 

 form within the yolk a syn- 

 cytium. Afterwards, in the later 

 stages, these division-cells, as 

 they may be, though somewhat 

 incorrectly, regarded, move 

 nearer the periphery and arrange 

 themselves into a plane parallel 

 with the surface (Figs. 506, A, 

 507, B). Continuing to divide, 

 they reach the surface and fuse 

 with the peripheral protoplasmic 



layer (Figs. 506, 

 Then follows the 



B, 507, C). 

 division into 



single cell-territories (Figs. 506, 

 .B, 507, C), corresponding to the 

 D division-nuclei, through the ap- 

 pearance of furrows which pass 

 in from the outer surfaces of the 



FIG. 506. Four successive stapes in the forma- egg into the interior and gradll- 



tion of the blastoderm of r,ti/i /,/,<>! i;,i,iitoria ,, . ,, , . 



(the figures represent segments of cross-sections ally penetrate the entire keilll- 



through the fly's egg) : A, the nuclei of the divi- , ,,, T , , . , , 



sion-cells have arranged themselves parallel with hautblastem. Ill tlllS Way the 



the outer surface of the egg. Jj, the division-cells <, ,, , , . , .... 



fused with the " keimhautblastem." C, the outer SUl'tace OI the 6gg IS COVCred With 



surface becomes furrowed by indentations; all -,1 T ,\ i 



the nuclei of the blastoderm-cells in process of & n epithelium (blastoderm). In 



division. D, the blastoderm-cells form a high cvl- TI i 



inder-epithelium : b, "keimhautblastem"; bs, many insects the SO-called llllier 



blastoderm -cells ; d, nutritive yolk; dz, yolk- a i TV ,i wl ,,i.u-| r , c ,j.,,,.., 57 /i?;,, K(\a 



cell: /*, so-called division-cell; Dinner "keim- keimhautblastem (Jb Ig. 50b, 



and t Hefder ra -"~ Afte ehmann ' from Korschelt Z), ,") is formed by the separation 



of a layer of protoplasm which 



contains larger granules and are accumulated between the blasto- 

 derm and the upper surface of the central nutritive yolk-mass. By 

 the addition of this plasmic layer the cells of the blastoderm increase 



