342 Journal of Comparative Neurology. 



His (i6) and Froriep (ly) and others do not agree with 

 this. They say that the optic fibers follow the lumen of the 

 optic stalk in their development from the retina to the brain. 



Robinson (i8) studied the relation of the optic nerve to 

 the optic stalk in mammals and confirms the results of W. 

 MiJLLER, Kolliker, Cajal, His and Froriep and says that the 

 nerve fibers grow inside of the optic stalk and among the cells 

 which constitute its walls. 



The conditions which I have found in the young at birth 

 indicate that the nerve fibers have grown between and around 

 the cells of the optic stalk. 



According to Kohl the optic nerve of the European mole 

 has as good a development in the 12 or 15 mm. embryo as 

 the one I have studied has at birth. 



As the nerve fibers leave the eye-ball a great many are seen 

 to decussate. This condition is found in both horizontal and 

 vertical sections. That is, fibers from one side of the retina 

 pass over to the opposite side of the optic nerve and vice versa. 

 Some of them, however, remain on the same side of the optic 

 nerve as that of the retina from which they originate. This 

 relation has been described by Kohl in the mole and by Cajal 

 (19) and NiCATi (21) in other vertebrates. 



The lens at this stage is found to be quite regular in shape 

 and almost uniform in size (Fig. 4 and 6). Its shape corres- 

 ponds very closely to that of the lens of any mammal at birth. 

 The average axial diameter is .019 mm. and transverse diame- 

 ter .024 mm. The ratio of the axial diameter of the lens to 

 the axial diameter of the eye is 1:30. 



In structure the lens differs widely from that of a normal 

 mammalian lens. It is composed of cells so crowded together 

 and possessing such large nuclei that they resemble cartilage 

 cells (Fig. 22, Plate XIX). Nothing is present which resem- 

 bles normal lens cells. The shape of these cells is very irreg- 

 ular as can be seen in Fig. 22. When examined with a high 

 power they show irregular processes extending in various direc- 

 tions. Frequently vacuoles are found within the cell. Figure 

 29 is a camera drawing of lens cells from an adult eye. The 



