BiaELow. — Development of Lepas. 
PLATE 1. 
Figures in this plate are all from living eggs, and represent stages between 
oviposition and the close of the first cleavage. The small circles represent the 
oil spherules which are embedded in the yolk. 
Fig. 1. Egg about thirty minutes after oviposition. Vitelline membrane and 
second polar cell have appeared. Yolk uniformly distributed in the 
egg. 
Figs. 2-5. Egg elongating. Protoplasm concentrating in upper half of the egg. 
Yolk becomes aggregated at the vegetative pole. Development of yolk- 
lobe. 
Fig. 6. Yolk-lobe has disappeared. Yolk radially symmetrical with reference to 
chief axis of egg. Vitelline membrane has assumed its definitive form. 
Fig. 7. Yolk moves to eccentric position with reference to the chief axis. 
Figs. 8-15. First cleavage. Time thirty minutes. Drawings made at intervals of 
about four minutes. Rotation of the dividing egg within the vitelline 
membrane. 
Fig. 16. One hour after close of first cleavage (Fig. 15). Yolk has returned some- 
what toward the vegetative pole. 
