326 MEAD. 



EXPLANATION OF PLATE XIX. 

 ChcBtopterus pergamentaceus Cuvier. 



Fig. 117. Side view, first cleavage ; the yolk-lobe, jv, in a very early stage. 



Fig. II 8. Same view, a little later. 



Fig. 119. Same view, later still. 



Fig. 120. Same view: yolk-lobe almost completely constricted off; nuclei 

 of two cells nearly reconstituted. 



Fig. 121. Same view : nuclei in resting stage; yolk-lobe has been resorbed. 



Fig. 122. From animal pole: transition from eight to sixteen cells. 



Fig. 123. From animal pole : 16-cell stage. 



Fig. 124. Same view : 32-cell stage. 



Fig. 125. Left side: just after 32-cell stage. 



Fig. 126. From animal pole : nearly a 64-cell stage. 



Fig. 127. From right side : same stage as last figure. 



Fig. 128. From left side: same stage. 



Fig. 129. Dorsal view: same stage. 



Fig. 130. Lower pole : same stage. 



Fig. 131. From vegetative pole : cross cells dividing obliquely ; one of the 

 polar globules within the rosette cell, p.g. 



Fig. 132. Right side of same egg: p.g., polar globule; one prototrochal 

 cell, cp^, dividing again. 



