320 



GENERAL ORNITHOLOGY 



PART II 



finally invested. The anatomy of the egg is Embryology. An egg, 

 or omim^ is simply the product of conception up to the time that 

 product acquires an independent existence ; while stOl connected 

 with the female tissue of the ovary, and before or after it amalgam- 

 ates 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 difference between the " egg " of a " viviparous " mammal and 



Fig. 103. — Urogenital 

 organs of male embryo bird ; 

 from Owen, after Muller. a, 

 kidneys ; &, ureters ; c, Wolf- 

 fian bodies ; d, their ducts, 

 to become sperm-ducts ; c, 

 genital glands, to become 

 testicles ; /, adrenals. 



Fig. 104. — Urogenital organs of 

 female embryo bird ; from Owen, 

 after Muller, a, kidneys ; "b. Wolf- 

 fian bodies ; c, genital gland, to 

 become ovary ; d, adrenals ; e, ure- 

 ters ; /, Wolfftau ducts, to disap- 

 pear ; g, Miillerian ducts, to become 

 oviducts.' 



Fig. 105. — Urogenital 

 organs of tbe domestic 

 cock ; after Owen, a, 

 testis ; 6, epididymis ; c, 

 sperm -duct or vas de- 

 ferens ; d, adrenal ; fc, 

 cloaca ; a;, kidney ; j/, 

 ureter. 



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, without anatomical connection 

 with the mother 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 essential germinative part of which is identical. 

 Appreciation of these facts, and a proper idea of the relations of 

 the mature sexual organs to the Wolffian bodies, is necessary to 

 any understanding of the parts and processes concerned in repro- 



