566 



MR. OWEN ON THE OVA OF THE ORNITHORHYNCHUS PARADOXUS. 



m. 

 n, n. 



Of 0. 



V- 



q- 



Fig. 3. 

 Fig-. 4. 

 Fig. 5. 

 Fig. 6. 



Fig. 7. 



The internal oblique muscle. 



The recti abdominis. 



The pyramidales. 



The cloacal passage. (The letter is placed on the retractor muscle.) 



The common outlet. 



The two smaller-sized ova of the Omithorhynchus paradoxus, (p. 560.) 



The two ova next in size, seen in situ in fig. 2. 



The larger ovum taken from the third specimen. 



The same ovum magnified three diameters, with the cortical membrane 



torn open, showing the vitelline membrane and its contents. 

 A small portion of the vitelline membrane, a, more highly magnified, with 



part of the germinal membrane, or membrana granulosa, h, adhering 



to its inner surface. 

 A portion of the ovary of an impregnated Omithorhynchus, magnified. 

 The capsule of the ovary. 



The laminated cellular substance, or stroma of the ovary. 

 The theca of a discharged ovisac, thickened, and encroaching upon the 



cavity from which the ovum had been expelled, forming a corpus 



luteum. 

 A small ovisac filled with its coagulated granular substance. 

 Part of a larger ovisac, with the granular substance removed, but the 



external granular stratum remaining. 

 Ovisacs artificially emptied, showing the state of the theca before the dis- 

 charge of the ovum. 

 The ovary of a Kangaroo six months after parturition, showing the cavity 



of the ovisac obliterated by its thickened parietes, nat. size. 

 . The ovary of a Rabbit two days after the coitus, showing its racemose 



structure, and the papillae of the Graafian follicles. 

 . The ovary of a Rabbit three days after the coitus, laid open. It is thus 



described by De Graaf : " Testiculus in quo tertio k coitu die foUicu- 



lorum crassities et cavitates, in quibus Ova delituerunt, apparent." — De 



Mulierum Organis, p. 412. tab. xxv., from which fig. 10. and 11. are 



taken. 



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