68 MR. T. K. GUNX OX THK 



Exceptions to the rule that breeding females possess but a 

 single left ovary must be very considerable. Since especially 

 looking for paired ovaries I have found them comparatively 

 common — the natural inference is that for many years I had 

 overlooked them. 



The number of examples of paired ovaries, apparently functional 

 and ready for ovulation in this series, negatives the idea of the 

 danger to life necessarily involved by the possession of a paired 

 generative system . If death were the common result of a right 

 and left ovary (with the corresponding ducts) it would seem likely 

 that specimens would have come to hand before now demonstrating 

 the pathology of the fatality and its mode of occurrence. I have 

 never handled such a bird \n the flesh, nor seen any reference in 

 print to dissections illustrating death from this cause. 



Is it not a reasonable conception that the nervous system 

 would govern the activity of the ovaries — and of course the 

 oviducts — dui-ing the period of turgescence associated with the 

 breeding season, utilizing the left ovary only, or the right ovary 

 only for the egg-supply and the other for a reserve — or in cases of 

 necessity utilizing both ovaries ? 



{a) In most of the later examples of paired ovaries in a state 

 of activity in my series — birds that were obtained in June and 

 early July and had then laid their full complement of eggs for 

 the season — all the evidence goes to show that though two ovaries 

 were present only one has been utilized for the production of eggs 

 (cf. V : 8'^) ; the other ovary developing eggs up to a point— the 

 ewgs then ceasing to grow in size and finally shrinking with those 

 in the working ovary to the small undeveloped ova common to 

 birds in the non-breeding season. 



In some of the earlier examples — birds obtained between March 

 and early May (cf. 5°; 1"^; 2''; 2")— both ovaries are well and 

 equally developed with eggs of approximately equal size in either 

 ovary — so that at this time it is impossible to guess which ovary 

 is to furnish the season's eggs, or whether the supply is to be 

 drawn from both. 



This seems to point to the nervous system determining which 

 ovary shall be finally selected for the year's output.^ 



Both ovaries are developed up to a certain point; and then 

 one comes to a standstill, while the requisite number of eggs 

 in the other continue to increase in size until they are ripe for 

 the oviduct. After they are shed both ovaries rapidly undergo 

 the normal process of involution and become comparatively 

 insignificant. 



According to this theory the regulating nervous stimulus could 

 be switched off one ovary nnd on to the other as best suited the 

 requirements of the organism. 



(b) If both ovaries are to share in the production of one clutch 

 of e^gs, then one can imagine each oviduct in turn being inhibited, 

 while an e^g is engaged in the duct of the opposite side, much as 



