IIO PL ATT. 



DESCRIPTION OF PLATE V. 



Secs. i and 2. Horizontal sections through the oculomotorius when it consists of 

 but one cell. 



Sec. 3. The oculomotorius completely established in horizontal section. 



Sec. 4. Cross-section, showing the median wall of the anterior head cavity (a) 

 giving rise to muscle cells that partly fill the cavity, showing also the rudimentary 

 muscle (mus. e.) of the mandibular cavity. 



Sec. 5. Cross-section, showing the relation of the external rectus muscle to the 

 rudimentary mandibular muscle (mus. <?). 



Sec. 6. Cross-section, showing that the cells of the external rectus muscle have 

 come to occupy the space occupied at an earlier stage by the cells of this muscle, 

 together with those of the mandibular muscle (mus. e.~). 



Sec. 7. The permanent trochlearis as it first appears. 



Sec. 8. Horizontal section, showing the fragments left by the primary trochlearis 

 when the nerve atrophies. 



