I I .
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cells (Karasaki, 1959). Some mitochondria are situated immediately
under the cortex, and are not displaced by the centrifugal force;
possibly they have a role in the contractions which occur in the cortex
FIGS. 1 , 2 . A Ciona egg seen immediately after centrifugation (inside the membranes) :
I = lipids; a = hyaline centripetal layer; p= granules; b= pigment a n d yolk granules
layer; m = mitochondria; c = hyaline centrifugal layer (Mancuso, 1959a).
F I G . 3. T h e ultrastructure of the hyaline centripetal layer (electron microscope) in a
centrifuged Ciona egg (Mancuso, in press).
at fertilization or during segmentation. The yolk granules are large and
elliptic; their surface looks smooth, and lacks the halo which has been
described in some yolk granules; e.g., in the ectodermal cells of