1865.] Prof. Owen on the Echidna Hystrix. 107 



trace of decidua in such impregnated uteri ; the smooth chorion was firmer 

 than that of uterine ova of Rodentia ; whence, and for other reasons given 

 in the Paper above cited, it was inferred " that the Monotremata were essen- 

 tially ovo-viviparous." 



The impregnated uteri of the Ornithorhynchus there described were of 

 females killed in the month of October. In the early part of December 

 young Ornithorhynchi, obtained from the nest, were transmitted to the 

 author : they were naked, blind, with short, broad, flexible, and softly 

 labiate mandibles, the tongue proportionally large, and reaching to near 

 the end of the mandibles ; the mouth not round, as in the mammary 

 foetus of Marsupials, but a wide transverse slit ; a pair of small patulous 

 nostrils opened upon the upper mandible, and between them was a small 

 prominence resembling the knob on the beak of the newly-hatched chick, 

 but softer, and lacking the cuticle, which had been torn off. There was 

 no trace of navel or umbilical cicatrix. 



The phases of the development of the mammary glands of the Orni- 

 thorhynchus were the subject of another communication, and, with 

 the peculiar formation of the mouth of the young animal, demonstrated 

 that it was nourished by milk as other mammals. The smallest of the 

 young of the Ornithorhynchus so obtained did not exceed two inches in 

 length. 



At the early part of the present year, the author received from Dr. 

 Mueller, F.B.S., of the Botanical Gardens, Melbourne, Australia, a female 

 Echidna (Ornithorhynchus Hystrix, Home, Echidna Hystrix, Cuv.), with 

 a young one, which the captor found adhering to the mother, as he sup- 

 posed, by a nipple. They were transmitted in spirits, and their description 

 forms the chief subject of the present communication. In regard to the 

 parent, the description is limited to the parts concerned in generation. 



The marsupial pouches are first described. These are two in number, 

 about 1 g inch apart, each with the aperture longitudinal and towards the 

 medial line, on the ventral integument, half an inch in depth and two-thirds 

 of an inch in length. The young Echidna, about one inch in length in a 

 straight line, could be received in a bent posture into the pouch, and might 

 cling to the fine hairs of that part by its claws ; but there was no trace of 

 nipple. Each mammary gland terminates by numerous ducts upon the fuudus 

 of the corresponding pouch. The structure of the gland, the ducts, the 

 surrounding muscles, and the pouch is described. The author next proceeds 

 to give an account of the internal organs of generation of the female Echidna. 



The left ovarium, as in the Ornithorhynchus paradoxus, was of an 

 oblong flattened form, developed from the posterior division of the ovarian 

 ligament and corresponding wall of the ovarian capsule ; it consisted of 

 a rather lax stroma, invested by a smooth, thin, firm " tunica propria," 

 which glistens where stretched over the enlarged ovisacs. Of these there 

 were five, of a spherical form, most of them suspended by a contracted 

 part of their periphery, not stretched into a pedicle, to the rest of the 



VOL. XIV. K 



