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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 Heitler 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 siirface and fuse 

 with the peripheral protoplasmic 

 layer (Figs. 506, B, 507, C). 

 Then follows the division into 

 single cell-territories (Figs. 506, 

 B, 507, C), corresponding to the 

 division-nuclei, through the ap- 

 pearance of furrows which pass 

 in from the outer surfaces of the 



FIG. 506. Four successive stages in the forma- egg into the interior and gradu- 



tion of the blastoderm of Callijihora vomitoria ,, ,-, ,, 



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



throuffh the tly's egg) : A, the nuclei of the divi- 

 sion-cells have arrange.! themselves parallel with 

 the outer surface of the eper. Ji. the division-cells 

 fused with the " k,-i ..... autblastem. 



-, , , -, ,, T , , , , 



hautblasteill. Ill tlllS Way the 



vson-ces r n ,-, -, -,1 



C, the outer SUl'tace Ot the egg IS Covered With 



^c^s o[ an epithelium (blastoderm). In 

 many insects the so-called inner 



l.l:ist..d..nii-rrlls; '/, nutritive yolk; f/s, yolk- u u .nl-mrlJocf pin " /'Fur 

 cell: /%, so-called division-ceU ; i, inner " kelm- V r 1 - 



!u!!ni^ie'r n ' "- AfterBk)chl " a " n ' fromKorschelt D, i) 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 



