318 Prof. Owen on the Ornithorhynclius. 



webs that extend beyond the nails when the animal swims, are 

 retracted, and the nails are exposed ; and from its attitude and 

 action it would be taken for a mole rather than a swimmer. As 

 it burrows it uses its tail, like a beaver, to beat the earth and 

 consolidate the sides of the burrow. 



The Ornithorhynchi are chiefly, but not exclusively, nocturnal ; 

 they are most vivacious by night, swimming then with the velo- 

 city of fishes, and moving about on land with remarkable agility ; 

 but the female, when she has young ones in the nest, will leave 

 them during the noon-tide heats and swim about. 



With regard to the generative oeconomy of the Ornithorhynchus 

 I may premise, that examination of the ovarium and of the ova, 

 both ovarian and uterine, had led me to the conclusion " that 

 they were, like the Marsupialia, ovo-viviparous ; and I conjectured 

 that the utero-gestation would be more prolonged, and the allan- 

 tois and umbilical vessels probably more developed*. But the 

 period of gestation remained to be determined, and the decisive 

 proof of ovo-viviparity, by the discovery of the foetus in utero and 

 the examination of its membranes, was a desideratum. This 

 M. Verraux appears not to have supplied, but he says : "The 

 number of Ornithorhynchi which I have possessed has perfectly 

 demonstrated to me that this animal does not laj'' eggs, as has been 

 supposed, but that it is ovo-viviparous. The ovaria, which form 

 part of my collections, sufficiently prove this.^' lb. p. 130. No 

 doubt, had M. Verraux obtained the decisive proof above referred 

 to, viz. the impregnated uterus, he would have mentioned itf. 

 He does not specify his physiological deductions from the ovaria, 

 but they were probably those which led me to the same conclu- 

 sion in my memoir in the Philosophical Transactions for 1834. In 

 that memoir I had stated that " the season of copulation was 

 probably at the latter end of September or beginning of October :" 

 but this point also remained to be determined by observation, 

 together with the manner of the coitus. The latter is thus de- 

 scribed by M. Verraux : — " Pendant le mois de septembre je 

 parvins h, decouvrir que I'accouplement avait lieu dans Peau. 

 Cache soigneusement sous un cabane fabriquee expres, et au fond 

 de laquelle il me fallait rester des nuits entieres sans oser me 



* Phil. Trans. 1834, p. 564. Art. Monotremata, Cyclopaedia of Anatomy. 



t It is to the absence of this proof that Dr. Carpenter appears to refer, 

 where he remarks, in his excellent ' Principles of Human Physiology,' 1842, 

 p. 40, " No positive evidence has yet been obtained that its young are born 

 alive." The minute size of the ovarian ovum and consequently of the vitellus; 

 the presence of small ova with a delicate chorion and without chalazae or shell, 

 in the uterine portion of the oviduct ; the absence of any shell-forming por- 

 tion of the oviduct, — all are elements of a body ofposifive evidence in favour 

 of the ovo-viviparity of the Ornithorhynchus, which needs only the disco- 

 very of the foetus in utero for decisive confirmation. 



