Jeknixgs. — Asplanchna. 



PLATE 3. 



Fig. 17. Eight side of the eight-ceil stage, same egg as that seen in Figures 13, 14, 

 and 15, showing the lateral extension and beginning of division of the 

 asters in c*'^ and c*'^. 



Fig. 18. Rigiit side of a slightly older stage than Figure 17, showing the com- 

 pletion of the division of the asters. In c*'i the line joining the asters 

 is lateral ; in c*'- it has already become oblique. 



Fig. 19. Right side of a stage later than that shown in Figure 18, containing nine 

 cells. The line joining the asters in c*-'^ lias become dorso-ventral, 

 while that joining those of c*i has become oblique. The cleavage of 

 c?*-i into d^-^ and d'''^ has occurred (compare Fig. 16), while d*-'^ is 

 still undivided. 



Figs. 20-25. Different views of an egg in the ten-cell stage, to show the position of 

 the spindles in relation to the exact form and dimensions of the cells. 



Fig. 20. Eight side of a stage later than Figure 19, but containing still only ten 

 cells. The line joining the asters in c*i has become dorso-ventral and 

 the spindle is formed between them. Likewise in c*- ; d*- has divided 

 into d-'-^ and r/^-*. 



Fig. 21. Anterior surface of the egg represented in Figure 20 ; the spindles occupy 

 the shorter axes of i''^ and b*-'^. 



Fig. 22. Left side of same egg showing the nuclear conditions in quadrant A. 

 The spindles are not yet formed. 



Fig. 23. Right face of optical, nearly sagittal, section, through quadrants B and 

 Z), from the egg shown in the three preceding figures, to exhibit the 

 exact dorso-ventral extent of the cells b^-^ and 6*-2, as compared with 

 the lateral extent of the same cells in Figure 21. 



Fig. 24. Dorso-ventral, approximately frontal, optical section of the egg shown 

 in Figures 20-23, showing the greatest dorso-ventral extent of the 

 cells of quadrants A and C, for comparison with the lateral dimen- 

 sions of tlie same cells, shown in Figures 20 and 22. 



Fig. 25. Posterior surface (quadrant D) of the egg shown in Figures 20-24. 



