DEVELOPMENT OF THE NERVOUS SYSTEM 



519 



The large epiphysial arch has disappeared as such and the 

 epiphysis now appears as a definite single evagination. Quite a 

 small cavity is present in the cephalic portion, however, while the 

 posterior portion has a well marked lumen. 



By Stage XII (figs. 4, 35) the habenular commissure is well 

 marked so that all the features enumerated by Minot ('01) as 



Fig. 5 A medial sagittal section of a 13 mm. larva. X 75. 

 Fig. 6 A medial sagittal section of an 8 cm. adult (full grown). 



X75. 



REFERENCES 



di. pi., diencephalic plexus 

 ep., epiphysis 

 hb., habenula 

 par., paraphysis 



p. c, posterior commissure 

 s. c, superior commissure 

 tel. pi., telencephalic plexus 



characteristic for this 

 physis has lengthened 

 in it. The post-velar 

 anterior part entering 

 plexus, the remainder 

 Both the cephalic and 



region have been described. The para- 

 and secondary diverticula are appearing 

 arch has further increased in extent, its 

 into the formation of the diencephalic 

 being, as yet, an unplicated membrane, 

 posterior portions of the epiphysis have 



iOTJKN.VL OP MORPHOLOGY, VOL. 25, NO. 3 



