60 K. KISHIXOUYE. 



with theii' «ur rounding protoplasm gradiuilly travel toward the 

 periphery of the egg through the yolk pyramids (PI. XII, tigs. 

 8, 9, 10). When about 30 in number, they all reach the surface. 

 \Vhen they are almost at the surface, the continuity of the perinuclear 

 protoplasm with the periplasm by means of pseudopodia-like processes 

 can be demonstrated on surface views. Figs. 3, 4, PI. XL are tw<^ 

 figures giving such views in which the radially arranged processes of the 

 perinuclear protoplasm (represented in the figures as dark lines) become 

 lost in the peri[)lasm whose polygonal markings are still visible. 

 Soon after such a stage the perinuclear protoplasm and the periplasm 

 are entirely mixed together forming a nucleated layer at the surface. 

 So far as my observations go, the nuclei emerge simultaneously all over 

 the surface of the egg — not, as Locy states, earlier at the animal pole 

 than at the opposite pole. When there are formed about a hundred 

 nuclei, this nucleated layer separates itself from the underlying yolk, 

 and then by the continual division of the nuclei the one-cell layered 

 blastoderm is established (PI. XIII, fig. 15). Coinciclently the poly- 

 gonal markings disappear and the egg recedes from the investing 

 membranes. Probably this is due to the swelling of the membranes 

 and not to the contraction of the egg. 



Whether the yolk still contains nuclei or is entirely free from 

 nuclei when the blastoderm is established has been a matter of 

 dispute. In my own sections, I could not at this stage detect an}- 

 nucleus at all in the yolk, thus confirming the views of Morin in 

 opposition to lîalfour's.* Yolk granules are, however, still aggre- 

 o^ated into masses. 



The change that comes next is of great importance. The cells of 

 the blastoderm when it is at first established are of uniform spherical 

 shapu throughout its extent. While; these cells gradually assume a 



* Balfour — Notes ou the Development of the Araneina, Quart. Jouru. Micr. Sei. XX. 



