AND OVIDUCTS IN THE AMNIOTA. 809 



hawk and some other Accipitres. When Nitzsch made his 

 anatomical contributions to Naumann's ' Naturgeschichte ' he 

 knew ah^eady of quite a number of cases of double ovaries. 

 R. Wagner* added to them in his Lehrbuch, and still more in his 

 BeitrJige. He described the cases of double ovaries accompanied 

 by double ducts ; he knew that vestigial ducts are much rarer 

 than ovaries, and was well aware of the fact that even in Accipitres 

 with double ovaries there may be no traces of a second duct, etc. 

 Stan ni us t added further cases in his Lehrbuch. It was, how- 

 ever, mainly owing to Wagner's lists that Dumeril could give a 

 general summary in Cuvier's posthumous edition of his ' Anatomie 

 comparee,' published in 1836. Owen + also felt justified in 

 summarising without referi-ing any more to special cases. On 

 p. 247 of his work he says : — " The symmetry [of the ovaria] is 

 soon disturbed by concentration of development in the left 

 ovarium, the right one remaining stationaiy, and ultimately, in 

 most birds, disappearing." On p. 249 : '' Subsequently the left 

 oviduct alone proceeds to gi^ow ; the right is stationary, or 

 shrivels ; occasionally it may be discovered as a rudiment in the 

 mature bird, but usually all trace of it has disaj^peared." 



Still further instances of abnormalities have been described 

 and even figured without adding to or upsetting the generalisa- 

 tions quoted above. In most of the general text- books and 

 others, which have occasion to mention these organs, the 

 quotation of certain birds has become a regular stock in trade, 

 always the same, copied from one author by the next, who in 

 turn is quoted as the original authority by the more popular 

 writer. 



So far as I know, I was the first to give a poFsible explanation 

 of the one-sided reduction, and I translate here what I wrote in 

 Bronn's ' Thierreich,' p. 842, published in 1890. "In all birds 

 only the left ovary is completely formed and functional ; the 

 right is present in most cases, and may even produce unripe eggs, 

 but these degenerate later and seem never to become free. In 

 correlation herewith the right oviduct undergoes early reduction ; 

 at most it persists towards the cloaca as a ligamentous strand, 

 may be even as a tube which opens into the cloaca. This one- 

 sided development of ovary and oviduct may be I'eferable to 

 saving of space. Two completely developed, hard-shelled eggs 

 would scarcely have room in the belly, and we may add that even 

 in the left oviduct two complete eggs seem to be very exceptional, 

 if such ever occur. In Reptiles, however, both ovaries and ducts 

 are equally developed." 



This idea could not have been expressed more guardedly than 

 by the following sentence in the ' Dictionary of Birds,' p. 783 : 

 " This one-sided suppression of the organs may possibly be 



* Wagnee; (1) Lelirbuch der vergleichenden Anatomie, 1834. 



(2) Beitrage zuv Anatomie der Vogel. Abhandl. Miincli. Akad. 



Wiss.ii. 1837, pp. 271-283. 

 t Stannius's Lelirbucli der vergleicbenden Anatomie. 1846. 

 X Owen : Anatomy ot Vertebrates, vol. ii. 1866. 



