ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 239 



that the result observed necessarily follows from the forced heavy 

 reproduction of the mother. Further experiments are necessary. 



When two full sisters from the series indicated are hatched from the 

 two eggs of a clutch, one of them behaves in a masculine manner. 

 Females hatched early in the season (when most males are produced) are 

 more masculine than their sisters hatched late in the season. Riddle 

 finds that if extracts from the ovary of a pigeon be injected into those 

 masculine females, they come to behave like females. Contrariwise, if 

 testicular extract be injected into those females that are acting like 

 females they come to act like males. The sex-behaviour of a bird is 

 probably determined by internal secretions from its sex-glands carried 

 to its central nervous system. It may be that the injected extract is 

 different from and superior to that naturally produced. 



Secondary Sex-characters in Fowls.* — A. Pezard has found that 

 when the ovary is removed from hens, spurs grow as in cocks. It 

 appears that the ovary has an inhibiting influence on the growth of 

 spurs. The growth that occurs after the removal of the ovary is con- 

 tinuous and regular, and its rate is as in cocks. The same is true of 

 plumage, the hen puts on that of the cock. Pezard concludes that 

 plumage and spurs are not strictly masculine characters like the comb 

 and the crowing. The development and turgescence of the comb in 

 cocks are conditioned by the internal secretion of the testes, but the 

 spurs and plumage are not. They are present potentially in the hens, 

 but are inhibited by the presence of the ovary. The capon and the 

 castrated hen may be almost undistinguishable. They approximate to 

 a neuter ancestral type without sex-dimorphism. From this the normal 

 cock and hen have been derived by addition and subtraction under the 

 control of the secretion of the gonads. 



Experiments on Oviduct of Fowl.f — Raymond Pearl and Maynie 

 R. Curtis have made numerous experiments which throw light on the 

 physiology of the oviduct of the fowl. Neither the ligaturing, section, 

 nor entire removal of the oviduct causes degeneration of the ovary or 

 prevents its further growth. The pressure of the enclosing funnel is 

 evidently not necessary to ovulation, for yolks are ovulated into the body 

 cavity after the ostium is sewed or ligatured, or after the entire duct is 

 removed. Internal pressure due to continued yolk-formation is probably 

 the most important factor in the normal rupture of the follicle, since 

 closing the funnel or removing the duct apparently does not greatly 

 delay ovulation. 



There are cases of. birds that have not been operated on, which have 

 normally functioning ovaries, and oviducts apparently capable of 

 functioning, which do not produce eggs because of some anatomical or 

 physiological condition of the mouth of the oviduct which prevents the 

 entrance of the yolk. 



The fate of yolks or eggs set free in the body cavity depends appar- 

 ently upon the physiological vigour of the bird. First, they may cause 



* Comptes Rendus, clx. (1915) pp. 260-3 (1 fig.), 

 t Jouru. Exper. Zool., xvii. (1914) pp. 395-424. 



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