4G8 
MR. W. H. CALDWELL ON THE EMBRYOLOGY 
that he had tried to discover the grounds for the generally-accepted belief that 
Ornithorhynchus both laid eggs and suckled its young. He found in females “ eggs of 
the size of a musket-ball, but without the hard outer shell, and, in the nest, young 
ones, and remains of a substance resembling egg-shell.” 
Three young Ornithorhynchi , found by Lieut. Malle in the nest, were sent home 
to Dr. Weatherhead ; two of these were given to Sir R. Owen, the third was given 
to M. Geoffroy. Sir R. Owen (45) discovered in these the caruncle on the bill. 
This striking structure, however, only confirmed Owen in his belief in ovi-viviparity. 
He wrote, 1834,* the Marsupialia and Monotremata “ may be regarded as an aberrant 
group of Mammalia, characterised by an ovo-viviparous generation.” 
Sir It. Owen’s researches were made possible by the enei’gy of Dr. George Bennett, 
who himself made several expeditions with the object of finding the early stages of 
Ornithorhynchus. Dr. Bennett (3, 4, 5, and 6) has accumulated a large number of 
interesting observations on the habits of the animal, and has never ceased trying to 
furnish Sir It. Owen with the material necessary for solving the problem of Monotreme 
generation. 
The next direct observation was made in 1847 by M. Jules Yerreaux (55) in 
Tasmania. He writes :—“ Le nombre d'Ornithorhynques que j’ai possede m’a parfaite- 
ment demontre que cet animal ne pond pas d’oeufs, mais qu’il est ovo-vivipare.” 
Sir It. Owen (47) reviewed M. Verreaux’s paper in 1848, and stated that he had 
calculated the period of uterine gestation at about six weeks ! In a foot-note, p. 318, 
Sir It. Owen, contradicting a statement in Carpenter’s ‘ Human Physiology,’ to 
the effect that there was no positive evidence in favour of the ovi-viviparity of Mono- 
tremes, says, “ The minute size of the ovarian ovum, and consequently of the vitellus; 
the presence of small ova, with a delicate chorion and without chalazse or shell, in 
the uterine portion of the oviduct; the absence of any shell-forming portion of the 
oviduct,—all are elements of a body of positive evidence in favour of the ovi- 
viviparity of the Ornithorhynchus, which needs only the discovery of the foetus in 
utero for decisive confirmation.” 
In 1864 Mr. George Rumby (52), a gold-receiver in Australia, obtained from some 
miners a living female Ornithorhynchus. This animal, shut up in a gin-case, laid two 
eggs which were “ white, soft and without shell, easily compressible, and about the 
size of a crow’s egg.” Mr. Rumby wrote in a letter that these eggs might be 
abortions caused by fear, and this suggestion was evidently accepted by Owen, who 
published the letter in 1865 (48). These eggs were also seen by Dr. John Nicholson 
(42), who wrote directly to Owen about them (48). Sir R. Owen in this paper, 
1865 (48), describes a mammary foetus sent to him by Baron Ferdinand von 
Mueller and Dr. Rudall, and, in discussing the uterine ova, describes the “smooth 
chorion as being firmer than that of Rodentia ; whence, and for other reasons ( vide 
‘ Phil. Trans.,’ 1834),” he still considered the animals ovi-viviparous. 
* ‘ Phil. Trans.,’ 1834, p. 356. 
