MEETINGS OF SOCIETIES. 343 
mode of depositing their eggs in the river, till he found it by 
a chance which could only have occurred by his camping 
on the bank of the river. His material for observation 
was obtained by an aboriginal camp, he having at one time 
as many as fifty aborigines at work for him. They got the 
porcupines for him, and some he employed searching weeds 
for the ceratodus. He proposed to describe the outlines of 
the embryology of the three main groups of animals which 
formed his scheme of work in Australia, and the embryology 
of which was, in the case of two, entirely unknown before, 
and in the case of marsupials unknown in the early stages. 
Marsupials were found all over Australia, and were in a way 
characteristic of it, as it was the only place where they had their 
habitat, except in South America and reaching to North America 
as far as Florida and San Francisco ; but they were essentially 
Australian. They were milk-giving animals, the same as the 
higher mammals, such as dogs and cats; but the difference 
between the marsupials and the higher mammals of the old 
world was that the young were born at a very early stage, and 
this fact carried with it a series of changes, such as differences in 
structure, which were characteristic of marsupials. But on the 
whole the marsupials did not differ to any great extent from the 
ordinary mammals, such as the cat, dog, or sheep. The main 
difference between them and the marsupials was that the egg in 
the uterus before the birth had no vascular attachment to the 
walls. There was no blood nourishment passing from the parent 
to the young animal. The egg of the marsupial was, in common 
with that of the higher mammals, a simple kind of food yolk. 
He then, by the aid of diagrams, described the structure of the 
egg of the marsupial. On the whole, the marsupial had a pecu- 
liar arrangement of the membranes, but the development of the 
ege itself was not essentially different from the development of 
the higher mammals. Hethen passed on to the development of 
the ceratodus. This animal was a representative of a series of 
animals which once were numerous in many parts of the world. 
At the present day there were three living representatives of this 
group of animals—the Dzpyoz, viz. the Ceratodus, tound in Queens- 
land, only in the Mary and Burnett Rivers; the Lepzdosiren, found 
in the Amazon; and the Profopterus, found in the Nile and 
others rivers in Africa. These three formed a class different 
trom all other animals, inasmuch as they possessed gills, and had 
the form of a fish in an adult state, and at the same time they 
possessed lungs. The structure known in other fish as the air 
bladder became in this fish highly vascular, and the aerated 
blood freshened by oxygen did not pass from the air bladder 
through the system, but passed direct to the heart, and there 
they had the first indication of two chambers in the heart, and 
they had for the first time‘arterial blood in the heart of a fish. 
Blood was found in an arterial state in animals with lungs, but 
in a veinous state in animals without lungs. His chief object 
in coming to Australia had been to obtain the development of 
