1851.] OF THE ROYAL INSTITUTION. 9 
WEEKLY EVENING MEETING, 
Friday, February 7, 1851. 
Tue Duxre or NortHuUMBERLAND, President, in the Chair. 
Proressor OwEn 
On Metamorphosis and Metagenesis. 
Tue Lecturer commenced by passing under review the Linnzan 
characters of Minerals, Vegetables, and Animals, and the subsequent 
distinctions which had been proposed for the discrimination of the 
two latter kingdoms of nature. After discussing those founded on 
motion, the stomach, the respiratory products, the composition of the 
tissues, and the sources of nourishment, it was shown that none of 
these singly, define absolutely the boundaries between plants and 
animals; it requires that a certain proportion of the supposed 
characteristics should be combined for that purpose. 
The individuals in which such characters are combined are specially 
defined members of one great family of organized beings, and the 
supposed peculiarly animal and vegetable characters taken singly, 
interdigitate, as it were, and cross that debatable ground and low 
department of the common organic world from which the specialized 
plants and animals rise ; and there are numerous living beings with 
the common organic characters that have not the distinctive com- 
bined superadditions of either group. 
Between the organic and inorganic worlds the line of demarcation 
may be more definitely drawn. The term ‘ growth’ cannot be used 
in the same sense to signify the increase of a mineral and of an 
organism. The mode of increase is different : there is a definite limit 
to it in the organic kingdom, and something more than mere growth 
takes place in the progress of an organism from its commencement 
to maturity. This was exemplified by reference to the human sub- 
ject, to the lion which acquires its mane, to the stag which gets its 
horns, and to the change of plumage in birds during the course of 
growth. Thechanges of form and character are still more remarkable 
in the kangaroo; and in the frog they are such as to have received 
the name of ‘ metamorphosis.’ 
The development of the frog was traced to its exclusion from the 
egg in the form of a fish, with external gills, a long caudal fin, and 
without legs. 
