JENNINGS: DEVELOPMENT OF ASPLANCHNA HERRICKII. 71 
or the lesser axis of the cells, so that from these cases no evidence on 
our question can be gained. But in later stages the crowding together 
of the cells results in greater or less alteration of the cell axes in rela- 
tion to the axes of the egg. In Figure 68 (Plate 8), for example, the 
long axis of the cell a?" is not parallel with that of d*?; the two are 
wedged apart dorsally by the cell d*", so that neither one points 
exactly to the animal pole of the egg. The two spindles are likewise at 
an angle with each other, and lie in the long axes of the cells, instead of 
exactly dorso-ventral. The same is true of the cells c^? and c™ in the 
same ligure. Again, in Figure 74 (Plate 9) the spindles of d and 
der, though in general direction dorso-ventral, form an angle with each 
other, the one in de being modified in position so as to lie in the 
longer axis of the cell, while the one in d' lies in the shorter axis of 
the cell. In the entoderm the same thing is strikingly true of the 
spindles shown in Plate 9, Fig. 79, and Plate 10, Fig. 83, for there the 
spindles form various angles with one another, all lying in the longer 
axes of the cells. 
jut these cases do not necessarily lead to the view that the form of 
the cell modifies even slightly the position of the spindle. It is 
possible that in each cell the axis of the spindle is determined other- 
wise, so that alteration of the position (not form) of the cell necessarily 
produces an alteration in the direction of the spindle. "Thus in Figure 
68 (Plate 8), if the cells d* and de. are ellipsoids of fixed form in 
which the two ends of the spindles have predetermined positions, in case 
the cells are forced apart, as in this instance by d*", tho ends of the 
spindles will be forced apart to the same degree. Though we know that 
the cells are not ellipsoids “of fixed form," yet we also know that the 
form of the cell is greatly influenced by the direction of the contained 
spindle, It is possible that the cytoplasm of the cell tends to group 
itself symmetrically about the contained spindle, so that the direction 
of the spindle is the primary factor, the fact that it lies symmetrically 
in one of the axes of the cytoplasmic mass being a secondary result. 
This becomes very probable when we examine from this standpoint the 
change of form of the very irregular cell des, shown in Plate 5, Fig. 
37 (surface view), and Fig. 38 (section), before the formation of the 
spindle, and in Plate 7, Fig. 54 (surface), and Plate 6, Fig. 48 (section), 
after the formation of the spindle. In this cell, before the forma- 
tion of the spindle, the shape is so irregular that it is not possible 
to distinguish a definite “ short axis," and no plane would divide the cell 
into symmetrical halves. But as the spindle is formed, the cytoplasm 
