MR. OWEN ON THE OVA OF THE ORNITHORHYNCHUS PARADOXUS. 565 



The nest was most carefully scrutinized by Mr. Bennett, but not the slightest trace 

 of egg-shell could be perceived in it. 



The principal points, therefore, in the generative economy of this paradoxical spe- 

 cies which still remain to be determined by actual observation, are, 



1st. The manner of copulation. 



2nd. The season of copulation. (This is probably at the latter end of the month 

 of September, or beginning of October.) 



3rd. The period of gestation. 



4th. The condition of the ovum both before and immediately after it has quitted 

 the ovisac. 



5th., The nature and succession of the temporary structures developed for the sup- 

 port of the foetus during gestation. 



6th. The exact size, condition, and powers of the young at the time of birth. 



7th. The act of suckling. 



8th. The period during which the young requires the lacteal nourishment. 



9th. The age at which the animal attains its full size. 



Description of the V LATE. 



Fig. 1. The ovary and expanded extremity of the Fallopian tube of an Ornitho- 

 rhynchus preserved in the Military Museum at Chatham, in which three 

 ovisacs, or Graafian follicles, had taken on the sexual actions. 



Fig. 2. The pelvis and surrounding parts of a female Ornithorhynchus, with the 

 urinary and genital organs in situ : the left uterus contains two ova. 



a. The left, a' the right, ovary. 



b. The two discharged ovisacs or corpora lutea, from which the ova, c, had 



escaped. 



d. The expanded orifice of the oviduct. 



e. The left uterus, showing its thickened parietes, and the depressions in the 



vascular internal membrane, in which the ova were lodged, e' the right 

 uterus. 

 /,/. The convoluted oviducts, or Fallopian tubes. 

 g, g. The ovarian and uterine ligaments. 

 h, h. The kidneys. 

 K, h'. The supra-renal glands. 



i. The urinary bladder, turned down; 



k. The rectum. ^ 



/. The external oblique muscle. 



MDCCCXXXIV. 4 D 



