216 



GENERAL ORNITHOLOGY. 



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

 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 diflerence is impressed hy 

 the greater complexity of structure acquired if the sex is to be male; a female being, anatomi- 

 cally and physiologically, simply an imperfect male, arrested at one stage of her physic;il 

 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, thougli 

 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 tlie 

 female, whose wolffian duct has disappeared, the mlillerian is the oviduct ; in the case of the 

 male, in which no mtillerian duct appears, the wolffian is the sperm-duct. The two are analo- 

 gous, not homologous (a good illustration — see p. 68). 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 spermatozoa, deposited in the cloaca 

 of the female, find their way up through her oviduct to the ovary, there to accomplish impreg- 

 nation 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. w6vj 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 finally invested. The anatomy of the egg is Embryology. An 

 egg, or ovum, is simply the product of conception up to the time that jiroduct acquires an inde- 

 pendent existence ; vi'hile still connected with the female tissue of the ovary, and before or after 

 it amalgamates with the male element, it is an ovarian ovum ; 

 more or less incompletely matured, it is an embryo or foetus, — 



the former term being commonly applied 



to the unhatched young of birds. The 



only difi'erence between the "egg" of a 



** viviparous" mammal and that of an 



"oviparous" bird, is in the albuminous 



and cretaceous envelopes of the latter, 



and its speedy expulsion from the body 



of the female to be hatched outside, with- 

 out anatomical connection with the moth- 

 er after the hard shell is formed ; whereas, 



in most mammals, the ovum is retained 



in a dilated part of the mtillerian duct 



(uterus or womb) until it "hatches"; but 



mammal and bird alike "lay eggs," the 



essential germinative part of which is 



identical. Appreciation of these facts. 



Fig. 104. — Uro-genital organs 

 of female embryo bird ; from Owen, 

 . after Miiller. a, kidneys; 6, wolf- 



and a proper idea of the relations ot the gan bodies ; c, genital gland, to 

 mature sexual organs to the wolflfian become ovary ; rf, adrenals ; e, ure- 

 ^ ters; /, wolffian ducts, to disap- 



bodiea is necessary to any understanding pear; .9, mUllerian ducts, to become 

 of the parts and processes concerned in oviducts, 

 reproduction.^ We have here to consider the permanent as distinguished from the transitory 

 kidneys, and may then recur to the subject of generation. 



I The matter may be further illustrated by the two figures borrowed from Owen (after Muller). In both figs., 

 the large dark masses, a, are the permanent kidneys, whose ducts, b in fig. 103, e in fig. 104, are the ureters, empty- 

 ing into the cloaca. In fig. 103, male, c is the wolffian body, whoee duct, d, persists as the sperm-duct, conveying 



Fig. 103.— Uro-genital 

 organs of male embryo bird; 

 ft-om Owen, after Muller. 

 a, kidneys: b, ureters; c, 

 wolffian bodies; cl, their 

 ducts, to be sperm-ducts; 

 e, genital glands, to become 

 testicles ; /, adrenals. 



