PLATE 2 



EXPLANATION OF FIGURES 



4 Drawing by C. Kellner of a reconstruction of a larva of Ophiura, ventral 

 view, at the stage in which the coelom and alimentary canal have been differ- 

 entiated. Above and to the right and left of the mouth opening, the small right 

 anterior enterocoele and the larger left anterior enterocoele are shown. These 

 enterocoeles are somew^hat obscured by the five lobed hydrocoele which, at 

 this stage, still retains its connection with the left posterior enterocoele. The 

 gut lies between the left and right posterior coelomic pouches and is in wide 

 communication with the former. The right posterior coelom (epigastric) still 

 retains its connection with, and shows its origin from, the ectoderm at a point 

 to the right of the blastopore scar. No attempt has been made to show the 

 large mass of yolk material and the mesenchyme cells which practically fill the 

 blastocoele. 



448 



