158 HISTOLOGY OF THE CENTRAL NERVOUS SYSTEM OF THE WEDDELL SEAL 



V. Issuing fibres of 5fch nerve. 



s.e.p. Superior cerebellar peduncle. 



p.l.b. Posterior longitudinal bundle. 



/. Tract of the fillet. 



8. Across the upper region of the pons : 



IV. Intercrossing fibres of 4th cranial 



nerves. 



n. IV. Root-bundles of 4th nerves. 

 s.p.d Decussation of superior peduncles 



of cerebellum. 

 /. Fillet. 



9. Across the posterior corpora quadrigemina 

 (mesencephalon) : 



Sy. Aqueduct of Sylvius. 

 f.ret. Reticular formation. 



p.l.b. Posterior longitudinal bundle. 

 s.c.p. Superior peduncles of cerebellum. 

 fify Intermediate and lateral fillet. 



t.d. Decussation of trapezium. 

 i.p.g. Interpeduncular grey matter. 

 n. III., n. IV. Nuclei of the 3rd and 4th cranial 



nerves. 



p.p. Crusta (pes pedunculi). 

 s.n. Substantia nigra. 

 C.Q.p. Posterior corpus quadrigeminum. 



10. Across the anterior corpora quadrigemina : 



p.c Posterior commissure of brain. 

 C.Q.a. Anterior corpus quadrigeminum. 

 n. III. Nucleus of 3rd nerve. 

 / 3 . Issuing fibres of 3rd nerve. 

 /. Fillet. 



PLATE II. 



A. Portion of the posterior part of the anterior 



lobe of the pituitary gland (Leptonychotes 

 weddellii). x 500: 



g. Large granular cells, staining deeply 



with eosin. 



sin. Sinusoidal blood-spaces, some of 

 them containing erythrocytes, 

 and occasionally showing an 

 endothelial lining (n.ep.) indi- 

 cative of a true capillary. 



B. Portion of the anterior part of the anterior 



lobe of the pituitary gland, x 500 : 



syn. Syncytium, including here and 

 there large isolated cells typical 



of the posterior part of the 

 anterior lobe (g). 

 v. True capillaries. 



C. Part of the pars intermedia of the pituitary 



gland, x 500: 



syn.p. Syncytium = fused spindle-shaped 

 cells with nuclei (n.) embedded 

 in the protoplasm. 



col. Colloidal substance at the edge of 

 the pars intermedia. 



D. Part of the posterior lobe of the pituitary gland : 



n.f. Neuroglia fibres. 



n. Nuclei of neuroglia cells. 



col. Isolated colloid masses. 



cl l . Large mass of colloid in a vessel (.). 



(ROY. soc. EDIN. TRANS., VOL. XLVIII., 866.) 



