Herrick, Brain of the Snake. 173 



tritive?) corpuscles near the epithelium and enters the radix lat- 

 eralis, which, at this stage, is well developed. There are still 

 mitosis figures adjacent to the ventricle in the tuber as well as in 

 certain parts of the olfactory epithelium. 



The radix lateralis may be traced back to the ventro-lateral 

 depression at the cephalic end of the pyriform lobe where a part 

 of the fibres seem to dip directly into the substance and another 

 part remains superficial and follows the depression named until 

 the point of union with the lateral aspect of the thalamus is reach- 

 ed. A part of the fibres pass into the latter' body to lose them 

 selves among its cells. 



PLATE XV. 



Fig. I. [206-3]. Section through the head of the youngest Euta'- 

 nia embryos passing through the lense capsule and primary optic vesicle. 

 The figure shows the connection of the lense capsule with the rest of the 

 cephalic sensory plate [ccph. s. />.) 



Fig. 2. [21 1-5]. Similar section of the second stage of Eutamia 

 (Plate XVI, Fig. 3.) The lense capsule has closed and the nasal sac is 

 invaginating. 



Fig. J. A portion of the brain tube showing the relation of spongio- 

 blasts and neuroblasts. Dividing neuroblasts (/') along the ventricular 

 surface give rise to neuroblasts [11) which make their way among the 

 spongioblasts (sp.) to the surface, there to form the neurons. 



Fig. .f.. P'rom a. Fig. 2. Numerous karyokinetic figures in the neu- 

 blasts are visible and one or two instances of mitosis in the spongioblast 

 nuclei (j/i .) Well developed neurons are also scattered near the sur- 

 face. 



Fig. J. From c, Fig. 2. The peripheral portion has already become 

 reduced to a semi-gelatinous stroma in which the neurons in various 

 stages are forming both axis cylinder and protoplasmic processes. 



Fig. 6. A portion of the eye and lense anlag in an embryo of the 

 same age as Fig. i. 



Fig. 7. A portion of the retina in Euta?nia embryos of the same 

 ages as Fig. 2, for comparison with the structure of the brain walls 



(Fig. 30 



Fig. S. Epithelium from the sensory plate near the nasal sac. 

 (Fig. 2.) 



