68 K. KISHINOUYE. 



yolk und mix themselves with the mesoblast cells (figs. 40, 41, mes). 

 This takes place chiefly in the dor.sum. These secondary mesoblast 

 cells may be compared to the fat cells of the spider. I was unable 

 to trace the fate of these cells, but tliink that some of them probably 

 become blood corpuscles. 



In early stages, just after the separation of the epililast and meso- 

 blast in the bJastoderm thickening, we find often some large cells in 

 the deep part of the mesoblast (fig. 24), find these gigantic cells seem 

 to play an active part in the multiplication of the mesoblast cells. 



Mesoblast and Segments. 



Tlie mesoblast after its formation extends very rapidly, chiefly 

 by division, which takes place mostly near the ventral median line. 

 The dorsal (distal) end of the mesoblastic somites is gradually pushed 

 towards the dorsal surface. In these parts the karyokinetic figures are 

 rareh' found, the cell multiplication taking place, as just stated, chiefly 

 by the division of cells in the ventral plate. The mesoblast cells in 

 the dorsal part of the second, third, and fourth appendage-bearing 

 segments become loose and spherical (fig. 39, 40). 



I can not say whether the metamerism arises from the change in 

 the epiblast or from that in the mesoblast. When the metaineric 

 division takes place, the mesoblast of the ventral plate is divided into 

 transverse segments between which the epiblast is grooved. 



The order of the separation of the segments is as follows ; — First 

 a common segment for the cephalic lobe and the first appendage-bear- 

 ing segment is cut off as the smaller anterior part of the ventral plate 

 (fig. 4). Then from the larger posterior portion the second, third, 

 fourth, fifth, &c. appendage-bearing segments are successively cut off. 

 When the sixth appendage-bearing segment is formed, the first 



