SEC. IV ANATOMY OF BIRDS 319 



part, leaving only a trace of their former existence in certain 

 vestigial structures (parova/ria, etc.) ; in the male, likewise, they 

 atrophy, but not to the same extent ; for a portion of the bodies 

 persists as an accessory (epididymal) portion of the testicle, and 

 their ducts persist as the sperm-ducts, or vasa deferentia. Mean- 

 while, in closest connection with the Wolffian bodies, appears a pair 

 of organs, the genital glands, for a while exactly alike. If the new 

 creature is to become female, the genital gland develops to a certain 

 complexity of tissue and becomes the ovary ; while a certain duct, 

 the Miillerian dud, developed coincidently to connect such ovary 

 with the cloaca, becomes the oviduct. In birds usually only one 

 ovary and oviduct (the left) becomes functional. If the new 

 creature is to become male, the same genital gland develops to a 

 higher degree of complexity, acquires a tubular structure, and 

 becomes the testicle ; it connects with remains of the Wolffian body, 

 and the Wolffian duct becomes the permanent sperm-duct, conveying 

 the product of the male function to the cloaca, just as the oviduct 

 conveysthe product of thefemale function to the same sewerage. Thus 

 the testicle of the male and the ovary of the female are homologous, 

 in fact primitively identical organs, upon which sexual difference is 

 impressed by the greater complexity of structure acquired if the sex 

 is to be male ; a female being, anatomically and physiologically, 

 simply an imperfect male, arrested at one stage of her physical 

 progress to male perfection of structure ; and the whole nature of 

 the female bears out the same relation of inferiority. But the 

 oviduct of the female and the sperm-duct of the male, though 

 physiologically identical, having the same function of conveying 

 the products of generation from the genital gland to the light of 

 day, are not anatomically the same ; for in the case of the female, 

 whose WolflBan duct has disappeared, the Miillerian is the oviduct; in 

 the case of the male, in which no Miillerian duct appears, the 

 Wolffian is the sperm-duct. The two are analogous, not homologous 

 (a good illustration — see page 103). But it must be further observed 

 that while the sperm-duct conveys only the masculine essence from 

 centre to periphery, the oviduct conveys the feminine material from 

 centre to periphery, and also the male essence in the opposite 

 direction ; for upon coitus, which is direct in all birds, the sperma- 

 tozoa deposited in the cloaca of the female find their way up 

 through her oviduct to the ovary, there to accomplish impregnation 

 of the ovarian ova, the fecund product then passing down by the 

 same avenue. All that relates to the mysteries of generation — both 

 the structure and function of the reproductive organs, and the 

 maturation of the product of conception, is properly Oology (Gr. liov, 

 oon, an egg) ; though the term is vulgarly used to signify merely a 

 description of the chalky substance in which the egg of a bird is 



