BIGELow. — Development of Lepas. 
PLATE 8. 
All figures drawn from sections ten micra thick. Vegetative (ventral) pole and 
blastopore at the /Je/t in views of sagittal sections. 
Fig. 66. 
Fig. 67. 
Fig. 68. 
Fig. 69. 
Fig. 70. 
Fig. 71. 
Fig. 72. 
Fig. 73. 
Parasagittal section of eight-cell stage, a little to the left of the sagittal 
plane, and corresponding to the stage shown in Figure 40 (Plate 5). 
Section, in same plane, of stage with fifteen blastoderm cells; the yolk- 
cell still in the stage of fourth cleavage. This stage corresponds to 
that of Figure 41. 
Parasagittal section of sixteen-cell stage, corresponding to that shown in 
Figure 45. 
Sagittal section of egg with twenty-eight cells in blastoderm; primary 
mesoblast cell (d5:2) in division ; entoblast nucleus preparing to divide. 
Compare with Figures 49, 50 (Plate 6). 
Horizontal section of same stage, seen from vegetative pole. 
Sagittal section of sixty-two-cell stage, counting two dividing primary 
mesoblasts (d63, d&*) as four cells. Same age as Figure 56 (Plate 7). 
Transverse section of egg in similar stage cut through the primary mes- 
oblasts and the posterior pair of “secondary mesoblasts ” (a7, c7-5), 
Section immediately anterior to the one represented in the preceding 
figure. The anterior “secondary mesoblasts ” (b75, b7:7) and the two 
entoblast cells (d%1, d°-2) are represented. 
