O. Gy. Dely szerk.: Vertebrata Hungarica 23. (Budapest, 1989)

Stohl, G.: Some remarks of the paired ovaries of birds (Aves) 29-32. o.

May be that similar processes had occurred in the evolution of the kiwis. In the evolutionary trend giving rise to the kiwis an inactivation of certain suppressor factors took place and it resulted in the appearance of organs characterising the pre-avian stage of Amniota vertebrates. As it is known, kiwis have beyond paired ovaries clitoris in their female reproductive system and a penis in that of the male one, and well-developed olfactory epithelium. It may be assumed that ancient, primitive characters can be acquired only secondarily by an organism of advanced type, and must not be considered as in unaltered form preserved primitive characters. Fig. 1. Ontogenetical development of the different types of birds' female gonads REFERENCES CORMAN, I. (1943): A basis for ostensible reversal of evolution. - Am.Nat. (Lancaster, PaJ, 7_7: 90-93. EYTON, T. C. (1835): Some account of a hybrid between the Cock Pheasant (Phasianus colchicus Linn.) and the Grey Hen (Tetrao tetrix Ej.). - Proc. Zool. Soc. Lond., 3: 62-63. KINSKY, F. C. (1971): The consistent presence of paired ovaries in the kiwi (Aptéryx) with some discussion of this condition in other birds.

1 J. Orn., Berl., 112

: 334-357. STOHL, G. (1970): Vergleichende Untersuchungen an Moschus- und Hausenten sowie deren verschiedenen Hybridkombinationen. - Állatt. Közl., 57: 145-155 (ungarisch mit deutscher Zusammenfassung). WELTY, J.C. (1964): The life of birds. - Constable et Co., London: 546 pp. WHITE, C. M. (1969): Functional gonads in Peregrines. - Wilson Bull., 81: 339-340. WITSCHI, E. (1935): Origin of asymmetry in the reproductive system of Birds. - Amer. J. Anat., Philad., 56: US141. YAMASHINA, Y. (1940): Studies on sterility in hybrid birds. I. Histological researches on the reproductive organs of hybrid birds from the family of Ploceidea. - Jap. J. Genet., 16: 97-105. Author's address: Dr. G. STOHL Zoological Department Hungarian Natural History Museum H-1088 Budapest Baross u. 13. Hungary