JE^'^-c<Gs. — Asplanchna. 



PLATE 8. 



Fig. 62. Dorsal view of an egg in approximately the same stage as that of Plate 

 7, Figure 61. Tlie four small unlabelled cells at the pohit of meeting 

 of the four quadrants are a"i'^-f/'i6. About 69-cell stage. 



Fig. 63. Ventral view of the egg shown in Figure 61, exhibiting the nearly com- 

 plete enclosure of the entoderm (to which the cell d^'^ belongs) by 

 the ectoderm. 



Fig. 64. Sagittal optical section of the egg represented in Plate 7, Figures 55, 56, 

 and 59. The cloud of granules in the entoderm cell cf'^ now sur- 

 rounds the dorsal aster of the spindle of the seventh cleavage. 



Fig. 65. Sagittal optical section of the egg represented in Figures 61 and 63, 

 showing the completed seventh cleavage in the entoderm; the cloud 

 of granules forms a ring around tiie nucleus in the smaller entoderm 

 cell (P'-. The ring being cut twice, appears in the form of two groups 

 of granules, one anterior, the other posterior to the nucleus. 



Fig. 66. Posterior view, showing the seventh cleavage in quadrant D. 



Fig. 67. Left posterior view; tlie seventh cleavage nearly finished in quadrant D; 

 the sixth not yet finished in quadrant A. From the egg represented 

 in Figures 61, 63, and 65. Sixty-nine cells. 



Fig. 68. Posterior view of a later stage than that represented in Figure 67. The 

 line separating f/^" and d'-^'- is the posterior median line ; the spin- 

 dles are seen to be arranged symmetrically with respect to this line, 

 so that the cleavage is becoming bilateral. The entoderm is entirely 

 covered by the ectoderm ; the region where a''-^ and d^-^ are in con- 

 tact shows the place where the entoderm cells formerly occupied the 

 surface. 82-cell stage. 



Figs. 69-74 give different views of the same egg, a 94-cell stage. 



Fig. 69. Anterior surface, showing the finished meridional cleavage forming the 

 cells G^ii-c^-ii, a^-^ -c^-'^, a^-i5_(.s-io^ and a^-i^-cS-is^ and tlie spindles 

 for the equatorial cleavage of a'-^-c''^ and a'-' -c'"'. 



Fig. 70. Right side of the egg shown in Figure 69. 



