48 HYPOPHYSIS->'OVARY ^OVIPOSITOR II 



had already shown that, within a test period of 44 hours, 

 the numbers of newly-formed basophil cells was subject to 

 considerable fluctuation, but the place where they occurred 

 was always the same. 



In all these experimental animals the pars anterior was 

 clearly divided, as regards colour, into two halves, one lying 

 obliquely behind the other. The anterior half remained 

 acidophilic; the posterior half, though not always sharply 

 outlined against it, was distinctly separate, at the back, from 

 the lobus intermedius, and contained basophil cells. It is 

 exclusively in this zone, running obliquely through the hypo- 

 physis, that the changes occur which, either directly or in- 

 directly, are caused by the exogenous hormone stimulus, and 

 which synchronise with the changes in the ovary and with 

 the reaction of the ovipositor* There is periodic alternation 

 of acidophil and basophil cells. For this reason we felt 

 justified in calling the region in question the " gonad atrophic 

 zone". 



Two observations support this view. In the first place 

 ^ the male bitterling has a considerably smaller anterior lobe 

 than the female. In the male, too, the gonadotropic region is 

 I far less developed. The sexual organization of the male does 

 / not require such an extensive gonadotrophic zone; testicular 

 N| activity covers a much longer period (autumn and winter) 

 I anxl the stimulus is, therefore, much weaker per unit of time 

 j than in the female, which, during the spawning season, has 

 to put the whole of its sex-apparatus into action quickly. 

 A second point in favour of our view is based upon the 

 communication by MATTHEW (1936), who described the 

 seasonal changes of the hypophysis in Fundulus, and observ- 

 ed that from September to .December the cells of the "Ueber- 

 gangsteil" (by which is meant the gonadotrophic region; vide 

 p. 47) are acidophilic, whereas during spawning time (from 

 May to July) they are chiefly chromophobe cells. When we 

 reflect that the chromophobe phase represents part of the 

 restitution phase of the pituitary cells, it is evident from his 

 communication that this part of the hypophysis plays its 

 part in the phenomena of the spawning period. 



