THE PINEAL SYSTEM OF AMPHIBIA 



225 



stalk with the roof of the diencephalon, to which it is attached in the 

 usual situation between the habenular and posterior commissures. The 

 superficial or distal wall of the end vesicle is formed by a single layer 

 of epithelium, whereas the deep or proximal wall shows two or three 

 layers of nuclei ; the inner ends of these cells in some specimens, e.g. 



c + p.i.r 



,v.c. 



>0 x<os77^ v- 



pig. opt.n 

 B 



Fig. 159. 



A — Proteus — Adelsberg grotto, reduced. The lateral eyes are invisible externally. 



There is a small pear-shaped pineal organ within the cranial cavity. 

 B — Vertical section, through one of the rudimentary lateral eyes. 



opt. n. : optic nerve; p.c.+p.i.r. : pars ciliaris+pars iridica retina;. The lips 

 of the optic cup meet in front owing to the absence of the lens. p'.g. : pig- 

 ment ; v.c. : vitreous cavity. Arrest of development has taken place at an 

 early stage, and the retina is unusually thick. 



(After Semper.) 



Salamander maculosa and Proteus anguineus, contain pigment granules ; 

 and in a specimen of Necturus described by Kingsbury (1895), two or three 

 medullated nerve-fibres on each side were seen by him to pass from the 

 brain into the epiphysis. Whether these nerve-fibres were efferent 

 fibres passing from the brain to the epiphysis or afferent fibres passing 

 from a vestigial sensory vesicle to the brain is a problem regarding the 

 solution of which we have no direct evidence which will help us to come 

 to a decision. The presence, however, of nerve-fibres passing between 



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