66 



HYPOPHYSIS->OVARY-> OVIPOSITOR 



nervous stimuli operate upon the sexual-endocrine organi- 

 zation. In our experiments with hormones added to the water 

 we accordingly assumed that these hormones, after being 

 taken in through the gills, reached a nervous centre via the 

 blood, and only thence stimulated the hypophysis to the 

 secretion of gonadotropic hormones. As the restitution of 

 ova is dependent upon and proportionate to the quantity of 

 corpus luteum hormone produced, we suspected that this 

 hormone is related to the nervous system which then stimu- 

 lates the hypophysis via the brain. On the basis of these 

 considerations we also studied the innervation of the hypo- 

 physis in the bitterling. Bretschneider observed this inner- 

 vation from serial sections after silver-impregnation of both 

 the brain and the hypophysis. 



b. Central tracks (Fig. 54A). 

 The principal nerves, such as the tractus praethalamo-saccu- 

 laris €t hypophyseos, emerge from the hypothalamus at the 

 front, through the hypophysial stalk, and may be followed 



cl factory tract 



a fermir)alis / , 



nucleus ' ^ 

 praeopt/cus 

 sex. centre(?J 



tract. praethal. saccul.'^ 

 et hypophys. 



fasciculus 



longitudinalis 



~-tect. optic, tracts 



A. Innervation 



Fig. 5 4 A. Innervation of the hypophysis in Rhodeus amarus; 

 central tracts. 



from the nucleus praeopticus (in which the nervus terminalis 

 ends). The nerves which penetrate the stalk proximally 

 originate in the olfactory tract. This runs dorsally and later- 

 ally from the nucleus praeopticus to the corpus striatum, and, 

 from here, as tractus striothalamicus et hypothalamicus, 

 reaches the hypophysis. Shorter tracts penetrate the caudal 

 side of the stalk and may be followed as far as the fasciculus 



