AND MAMMARY FOETUS OF THE ECHIDNA HYSTRIX. 
677 
A warm-blooded air-breather, compelled to seek its food in water, could not safely 
carry the progeny it had brought forth in a pocket beneath its body during such quest ; 
and all observers have noted the nest-making instinct of the Platypus , in which tempo- 
rary and extraneous structures only the young have hitherto been found *. Mr. George 
Bennett states that the nest “ appears to be found about the time of bringing forth the 
young, and consists merely of dried grass, weeds, &c.” f 
Whether the Echidna prepares any extraneous nest is not known. The specimen 
transmitted to me by Dr. Mueller was caught in the hollow of a prostrate “ cotton tree.” 
Being a terrestrial animal, she can carry her young about habitually concealed or partly 
sheltered in her pouches ; and the present observations show the nearer affinity in this 
respect of the Echidna to the marsupial Ly encephala. The Echidna may further mani- 
fest this relationship by the more minute size of the young when born and transferred 
to the pouch, as compared with the Ornithorhynchus ; but the size of the new-born or 
newly-excluded young of that monotreme is unknown. The smallest specimen of a young 
Ornithorhynchus which I have yet seen is that (Plate XLI. fig. 5) to which allusion has 
been already made as being about two inches in length in a straight line. 
The following are the comparative dimensions of this, and of the young of the female 
Echidna (ib. fig. 3 (magn.), Plate XL. figs. 6-10 (nat. 
size)), the subject 
of the present 
communication : — 
Young 
Young- 
Ornithorhynchus. 
Echidna. 
in. 
lin. 
in. 
lin. 
Length from the end of the upper jaw, over the curve of 
the back, to the end of the tail .... 
3 
9 
1 
10 
Length from the same points in a straight line along the 
abdomen 
2 
1 
1 
1 
Greatest circumference of the body .... 
2 
9 
1 
o x 
Length of the head 
0 
8i 
0 
4 
Length of the upper mandible from the gape . 
0 
3 
0 
1* 
Breadth of the upper mandible at the base 
0 
4 
0 
1 
Length of the tail from the vent 
0 
4± 
0 
1 
Breadth of tail at the root 
0 
4 
0 
X. 
Length of the fore foot 
0 
3 
0 
2 
Breadth of ditto 
0 
0 
H 
Length of the hind foot 
0 
4 
0 
l 
Breadth of ditto 
0 
3 
0 
H 
The circumstances under which this young Echidna 
was obtained are given in 
a letter 
by the captor, Mr. G. O. Harris, to Dr. Mueller, dated “ Colac Forest, August 31, 
1864.” 
* Tom. cit. p. 533. f Trans. Zool. Soc. vol. i. pp. 247 & 253. 
+ This might have been more before the body had become somewhat dried, or shrunk in rwt*, 
