G84 PEOFESSOE OWEN ON THE MAESUPIAL POUCHES, MAMMAE Y GLANDS, 
during the night. In the course of the day the creature Was killed by a would be scien- 
tific friend of mine, with the intention of preserving its skin ; and on opening the bod)' 
the ovaries wore found to be clustered with ova in different stages of growth ; but none 
of them so large as the eggs which were laid. These eggs were white, soft, and with- 
out shell, easily compressible, and about the size of a crow's egg. 
"Not being sufficiently versed in the subject I am not prepared to say whether these 
e gg s mi g ht not have been abortions caused by fear, but there was no appearance on the 
surface of their ever having been vascularly connected with the maternal uterus, and 
reviewing all the facts observed I should undoubtedly say that the animal was oviparous. 
" I am, dear Sir, 
" Yours faithfully, 
(Signed) « Geo. J. Pojmby." 
Dr. Mueller, in transmitting me the foregoing copv of the Gold-Receiver's letter, 
writes (November 25th, 1864), "Since writing to you by last mail I have received the 
enclosed letter respecting the Ormthorhynchus having proved to be < oviparous: How are 
all these statements to be reconciled'?" 
Assumingthe fact of the oviposition, in the month of December 18G3 (Dr. Nicholson 
writes of the occurrence as having happened "about ten months" before the date of his 
letter, September 21, 1804) by a female Ornithorhynckus, of two ova, about the size of a 
crow's egg, " white, soft, compressible, without shell or anything approaching to a calca- 
reous covering," the question is— What did they contain 1 Had the unvascular chorion 
been cut or torn open, an embryo or a yelk might have been seen. Better still would it 
have been if both ova had been at once immersed in a bottle of whatever colourless 
alcoholic liquor might be at hand. Probably no medical man had ever an opportunity 
01 a chance of settling a point in Comparative Physiology of more interest, and with less 
trouble, than the gentleman who was privileged to be the first person to see and handle 
the new-laid eggs of the Ornithorhynchus paradoxus. 
For the reasons given in my Memoir of 1834*, I concluded that the Monotremes were 
not "oviparous" in the sense of the author of the memoir in the 'Annates des Sciences 
Naturelles,' vol. xviii. (1829)f, but that they were ovo-viviparous, and in a way or degree 
more nearly resembling the generation of the Viper and Salamander than occurs in the 
Marsupial ia. 
The young Viper is provided with a specially and temporarily developed promaxillary 
tooth for lacerating the soft, but tough, shell of its egg, and so liberating itself^. From 
this analogy I imagine that the young Monotremes may be provided with a horny or 
epidermal process or spine upon the internasal tubercle, for the same purpose. This 
temporarj tubercle is obviously homologous with the hard knob on the upper mandible 
* " On the Ova of the Ornithorh/nckm paradoxus," Philosophical Transactions, vol. exxiv. p. 555. 
t R. E. Grant, « (Baft de rOrnithorhynqnc," Ann. des Sciences Nat. 1829. 
% Weiniand, in Muller'8 Archiv fur Physiologic, 1841. 
