No. 611] GENESIS OF ORGANIZATION OF INSECT EGG 645 



These have been considered symbiotic bacteria, but their 

 true nature remains yet to be definitely established. 



3. Cleavage 



The first cleavage nucleus of the beetle's egg lies some- 

 what anterior of the center in a small island of cytoplasm 

 that is continuous with the cytoplasm that surrounds the 

 deutoplasmic bodies (Fig. 1, gn). During early cleavage 

 no cell walls are formed, but after each division the 

 daughter nuclei move a short distance apart and then 

 divide again. Successive divisions and migrations of the 

 cleavage nuclei (Fig. 3) finally result in the production of 



hundreds of nuclei, which come to lie just beneath the 

 cortical layer of cytoplasm, and are each surrounded by 

 an irregular mass of cytoplasm. The fusion of these 

 cytoplasmic masses with the cortical layer then takes 

 place, followed by the intervention of cell wall>, t1uis form- 

 ing a blastoderm of a single layer of cells, eacli of wliich 

 contains a cleavage nucleus, part of the cytoplasm which 

 it brought to the periphery with it, and a portion of the 



Stsber. bdhvi. GeselJsch. Wiss. Prag.; Sulc, 1910, ibid.; Merceir, 1907, Arch. 

 Frotistenk., Bd. 9; Pierantoni, 1910, Zool. An^., Bd. 36; Buchncr, 1912, 

 Arch. Protistenk., Bd. 26 j Tanguary, 1913, Bull. III. St. Lab. Nat. Hist., 

 Vol. 9 ; Hegner, 1915, Journ. Morph., Vol. 26. 



