G6 MR. T. E. GUNN ON THE 



details of the parts as he found them. Eev. F. C. R. Joiirdain * 

 suggests that Newton's exceptions might have been drawn from 

 a German source t. 



Professor Taschenberg, the writer of the article referred to by 

 Jourdain, says : — 



" It happens not very rarely that remmns % of the right ovaiy 

 are retained, especially in the sparrow-hawk and buzzards, 

 much more irregularly in other accipitres, and still more 

 rarely in the owls." 



Ceteris parihiis, a bird possessing two functional ovaries is clearly 

 more fitted for the reproduction of its kind than the bird with 

 only one. If disease or injury destroys the one ovary and spares 

 the other, the bird can still fulfil the chief duty of its life, 

 the bearing of ova. If the one ovary becomes exhausted (e, g. 

 destruction of first nests) the other would act as a reserve to 

 draw on in cases of necessity. If the fittest female is to survive 

 in the long run, one would suppose that the bird that possessed 

 the two complete genital tracts, the foundations of which were 

 laid in the very early embryo, would surpass its fellow which had 

 squandered fifty per cent, of its reproductive capital while still in 

 the shell. That that is not the case we know. 



Speaking in general terms, the rule holds good that adult 

 females have but one ovary and one oviduct, those on the left 

 side. 



Why has the second ovary been abolished ? 

 It has been suggested §, with some show of probability, that the 

 suppression is in connection with the passage of the egg through 

 the oviduct; that the danger involved by two eggs engaging 

 simultaneously in the two oviducts would be very great, and 

 would lead to'fracture of the delicate shell, or rupture of the walls 

 of the containing duct ; to peritonitis, intestinal obstruction or 

 some such cfdamity, and in any event death. 



If such an accident — a fully-developed egg in the lower part of 

 either oviduct at the same time — were to happen, no doubt the 

 results would be untoward. A Guillemot with two full-sized 

 eggs in its abdomen would presumably burst. 

 " But is it necessary to suppose that such a sequence would follow 

 the presence of two separate genital tracts ? 



I think not. The number of cases collected in this paper goes 

 far to prove that death and disaster are neither the necessary 

 nor even the common result of paired ovaries. It is contradicted 

 by the frequency with which the Falconida^ are found with paired 

 ovaries which are obviously functional. That a single ovary 

 permits the bird to perpetuate its kind is true enough. The 



* ' Britisli Biids,' Dec. 1910, p. 218. 



f ' Natniiiesshic-hte der Vogel Mitteleuropas,' vol. i. p. 60, 1905. [Dr. Gadow, m 

 Bvonii's 'Tliier-Reicb, Vogel,' p. 842, quotes from Staunius, and adds instances from 

 liis own observation of the persistence of the right ovary, particularly in diurnal 

 lirds of prey.— -Editor P. Z. S.] 



X Italics are mine (T. E. G.). 



§ Newton, ' Dictionary of Birds," p. 783. 



