5i8 



LOCY. 



[Vol. XI. 



seek. The condition of the neural folds in this animal is very 

 unusual : when first formed they are lateral, wing-like expan- 

 sions, extending along each side of the embryo, overhanging 

 the yolk (cut 5). No sooner are they formed than they become 

 ventrally curved, and, in this way the most clearly segmented 



'Wyutis 



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s 



f 



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Cut s. — Twelve transverse sections of the embryo of the preceding cut. x about 30 diameters. 

 The neural folds are expanded laterally beyond the body and ventrally curved. 



parts of the embryo are brought ventralwards, and this 

 accounts for the metameres being most distinct when viewed 

 from the ventral surface. 



Figs. 28 and 29 represent two views of the same embryo; it 

 is an older stage than that represented in Fig. 27. The neural 

 folds are now fully formed and their ventral curvature is very 

 marked. In Fig. 28, the optic vesicles (o/>) are seen on each 

 side of the central tongue-like process to which attention has 

 already been called. 



