444 W. H. GASKELL. 



the course of the nerve as seen in the whole series of sections. The part of 

 nerve shaded was the only part visible in this particular section. 



Fig. 28. — Diagram of the pineal eye of Animococtes as restored, to show 

 its Arthropod characteristics. For the sake of clearness most of the pigment 

 surrounding the nerve-end cells is not shown in the diagram, but its limits 

 only are indicated by the lines of black dots. 



Fig. 29. — Diagram to show the transformation of the walls of the Crustacean 

 cephalic stomach into the lining epithelium of the cavities of the brain of 

 Ammocoetes. Red represents the contour of the cephalic stomach. Yellow, 

 the contour of the lining epithelium of the cavities in the brain of Ammocoetes 

 if the choroid plexuses were unfolded [cf. Ahlborn (3), fig. 41, PL xvi]. Black 

 indicates the position of the principal nervous structures in relation to the 

 Crustacean cephalic stomach, and to the brain-cavities respectively. 



