34 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
cells of quadrants A, B, and C the spindles are not in the short axes, as 
in d°*, since these cells are not nearly so broad as that one, while the 
dorso-ventral dimension is about the same or greater (Plato 4, Figs. 30 
and 32). Figure 41 (Plate 5) shows the process of cleavage in these 
cells, while Figure 45 (Plate 6) shows the cleavage concluded. 
The division of the second layer follows upon that of the fourth, and 
again in the order c9?, 052, 4. The division is here meridional, as it is 
in the corresponding cells of the quadrant D, and equal, as it is not in the 
corresponding cell ot the quadrant D. (See Figs. 39, 40, 43, and 44.) 
Next follow the divisions of the cells of tho first layer, in the same 
order as in the previous cleavages, and, slightly later, the divisions in 
the third layer, also in the same sequence. The cleavages here also are 
meridional and equal. 
The nuclear conditions leading to these cleavages are shown in Figures 
39, 40, 42 (Plate 5), all from the same egg. A somewhat later stage 
is shown in Figure 42, which exhibits the conditions in the quadrants 
A, B, and C at a time when the divisions just described are completed 
in most of the cells. All the divisions are nearly finished except in the 
cells of the third layer (a59— 099), which still contain spindles. This 
view shows also another peculiar fact. During the cleavages the cells 
about the dorsal pole of the egg have shifted, and the cells a9" and c9 
have pushed ventrad to such an extent that on the right side tho cells 
c5? and b8 have become completely separated, a part of the cell cê" 
lying between them. This condition is only transitory, however; the 
cell c is very soon pushed dorsad again, and the cells of the third layer 
again form a continuous row. (Compare Figure 47, Plate 6.) Figure 46 
shows the cells of the quadrant D at the close of this division, while 
Figure 45 is a view of the animal pole at the same stage. 
The features of the fifth clenvage may be summarized as follows. In 
the twelve cells of the three ventral layers, the asters separate after the 
fourth cleavage at right angles to the position of the preceding spindles 
and retain the position first taken ; the cleavage is therefore meridional. 
In all these cells the spindles are in the long axes of the cells. In the 
dorsal layer the asters at first assume the same position as in the othor 
cells, but later a rotation takes place, and the spindles when formed 
have a dorso-ventral direction ; the resulting division is equatorial. Tho 
5.4 
spindle is in the longer axis of the cells a5, 055, and c! 
720 „ in the shorter 
Axis in d. 
The division is unequal in the four dorsal cells of all the quadrants, 
and in all the cells of the quadrant D. In the other cells it is equal. 
