Fig. 23 A. 



SC 



MES 



i tkegmenting egg, seen from its lower pole, and illustrate 

 Tfour large figures are sections of the egg taken vertically 

 :aeti the formation of the mcsenteron. Notice the rotation 



ilsjN, mesenteron ; sc, segmentation cavity or blastocoel; 

 wli is at first vertical and subsequently antero-posterior ; 

 si uently vertical or nearly so. 



Between pages 112 and 113. 



