BIGELOW. Development of Lepas. 



PLATE 5. 



Figures from transparent preparations of entire eggs. Vegetative pole at the 

 left in figures which represent lateral views. 



Fig. 39. Eight-cell stage from animal pole. The seven " protoplasmic " cells are 

 in the fourth cleavage; the nucleus of yolk-cell (rf 4 ' 1 ) is preparing for 

 division. 



Fig. 40. Same egg in lateral view. Yolk at vegetative pole of cell d*' 1 . 



Fig. 41. Fifteen "protoplasmic" cells; tke yolk-cell (c/ 4 * 1 , mes-entoblast) divid- 

 ing. Lateral view. 



Fig. 42. Sixteen-cell stage from animal pole. Nuclei of all cells are in " resting " 

 phase. Primary mesoblast (d 5 * 2 ) separated from entoblast (</ 5-1 ). 



Fig. 43. Same egg viewed from vegetative pole. Oil spherules near lower surface 

 of the yolk-cell. 



Fig. 44. Sixteen-cell stage from animal pole. All cells, except yolk-cell (entoblast 

 c? 5>1 ) and the primary mesoblast cell (c/ 5>2 ), are undergoing the fifth 

 cleavage. 



Fig. 45. Same egg in lateral view. 



Fig. 46. Same stage from vegetative pole. The three mes-ectoblasts (compare 

 Fig. 43, a 5 ' 2 , 6 5 - 2 , v>- 2 ) contiguous to yolk-cell. 



NOTE. Cell a 5 ' 2 is represented as divided, and its derivatives should have been 

 labelled o-, a*-*. 



