CELL SIZE AND NUCLEAR SIZE ff 
Lillie (01) has shown that the spindle oscillates in the cell before 
coming to rest in its eccentric position; and in many cleavages 
in Crepidula the spindle may at first le out of its normal position 
and may move later into its proper place; and this applies not 
only to the eccentricity but also to the axial position of the spin- 
dle. Something outside of the spindle itself determines the posi- 
tion which it shall take in the cell, and this is as true of equal and 
alternating cleavages as of unequal and non-alternating ones. 
TABLE 2 
Sizes of macromeres and micromeres in Crepidula and Fulgur 
SPECIES MACROMERES DIAMETER | MICROMERES DIAMETER Raetiea 
Me | Me 
(| 1A4-1D 81 la-Id 30 Cantor cet 
2A-2D 80 2a-2d 36 ca. 10.6: 1 
3A-38D 76 | 3a-3d 33 Canh2 mle 
@Aplanaey seer 4D 66 4d | 38 Geis 25.0) gal 
4A-4C 60 | 4a-4e 42 GH. Bae oil 
5A, 5B 75 metay: Fir) 0) 60 Gis 1h.@) gu 
5C, 5D 68 5e, 5d 68 ca. il gi 
( 1A-1D 195 la-ld 69 ¢a, 22.0) 31 
(Caconvexaaaee 2A-2D 195 2a-2d 50 CH G8)3) oil 
3A-38D 195 3a-3d 50 Car OO ons L 
(|) 1A-1D 800 la-ld 80 | ea. 1000 : 1 
2A-2D 800 2a-2d 80 ea. 1000 : 1 
Fulgur carica. . 3A-3D 800 3a-3d 80 can OOO Rt 
4D 780 4d 130 Cas eZGucel 
| 4A4C | 740 4a—te 370 Can sonee! 
The third, fourth, and fifth cleavages of the macromeres of 
Crepidula and of other gasteropods are successively alternating 
in direction, and are notably unequal In the size of the daughter 
cells; while the sixth and all subsequent divisions of the macro- 
meres are more nearly equal than the preceding ones. The 
diameters of the cells formed by these cleavages and their approxi- 
mate ratios, in Crepidula and Fulgur, are shown in Table 2. 
In the structure of the macromeres there is no visible organi- 
zation which would explain why the first two cleavages of the 
ege are equal, the three following ones very unequal and subse- 
