216 GENERAL ORNITHOLOGY. 
product of the male function to the cloaca, just ine 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 difference is impressed by 
the greater complexity of structure acquired if the sex is to be male; a female being, anatomi- 
cally aud 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 ease of the 
female, whose wolffian 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 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 feeund.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 Odlogy (Gr. adv, 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 product acquires an inde- 
pendent existence ; while 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 fatus, — 
the former term being commonly applied 
to the unhatched young of birds. The 
only difference between the ‘‘egg” of a 
“viviparous” mammal and that of an 
“oviparous” bird, is in the albuminous 
and ecretaceous 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 miillerian duct 
(uterus or womb) until it ‘* hatches” ; but 
mammal and bird alike “lay eggs,” the 
Fig. 103. —Uro-genital essential germinative part of which is Fic. 104, — Uro-genital organs 
organsofmaleembryo bird; identical. Appreciation of these facts, of female embryo bird; from Owen, 
from Owen, after Miiller. : : : : after Miiller. a, kidneys; b, wolf- 
a, kidneys: b, ureters; c, aud a proper idea of the relations of the gan podies; c, genital gland, to 
wolffian bodies; d, their mature sexual organs to the wolffian become ovary; d, adrenals; e, ure- 
ducts, to be sperm-ducts; aA é ; ters; /, wolffian ducts, to disap- 
e, genital glands, to become bodies is necessary to any understanding pear; g, miillerian ducts, to become 
testicles; 7, adrenals. of the parts and processes concerned in oviducts. 
reproduction.1_ We have here to consider the permanent as distinguished from the transitory 
kidneys, and may then reeur to the subject of generation. 
1 The matter may be further illustrated by the two figures borrowed from Owen (after Miller). In both figs., 
the large dark masses, a, are the permanent kidneys, whose ducts, 0 in fig. 103, e in fig. 104, are the ureters, empty- 
ing into the cloaca. In fig. 103, male, c is the wolffian body, whose duet, d, persists as the sperm-duct, conveying 
