10 NOTICES OF THE MEETINGS [Feb. 7> 
The internal skeleton, like the external shape, is adapted for 
aquatic life. 
Only those parts are ossified which are to be retained in the 
mature state. The vertebre are at first biconcave, as in fishes, with 
invervening spherical elastic balls filled with fluid: they are converted 
into ball and socket joints by the ossification of the sphere, and its 
anchylosis to the back part of the vertebre. The pelvis and hind 
legs are progressively developed; and, whilst this change is pro- 
ceeding, the tail is undergoing proportional absorption. The chief 
change in the skull of the larva is operated in the lower or hemal 
arches and their appendages. The maxillary arch is widened and 
provided with teeth, and the horny mandibles are shed. The man- 
dibular arch retrogrades as well as expands. The hyoidean undergoes 
a remarkable change of size and shape, and the branchial arches 
are absorbed, excepting a small portion which is converted into the 
hinder ‘ horns’ of the hyoid for supporting the larynx. 
The scapular arch, which at first was connected with the occiput, 
whilst supporting the branchial heart — its primary function, begins 
as soon as the fore-legs bud out, to retrograde, and the sternum is 
developed to complete the ‘ point d’appui’ for the fore limbs. 
The food of the larva is chiefly the soft decaying parts of aquatic 
plants; it has a horny beak, a long alimentary canal disposed in a 
series of double spiral coils: but, as its frame undergoes the changes 
adapting it for life on land, and a purely animal diet, the mandibles 
are converted into jaws and teeth, and the long spiral intestine intoa 
short and slightly convoluted one. 
Soon after the external gills have reached their full developement 
they begin to shrink and finally disappear ; but the branchial circu- 
lation is maintained some time longer upon internal gills: by anas- 
tomoses between the principal branchial vessels these are converted 
into the aortic arches, carotids and subclavians ; the internal gills 
with the cartilaginous hoops supporting them are absorbed, and 
lungs and glottis for breathing the air directly are developed. 
Thus an animal formed for moving in water is changed into one 
adapted for moving and leaping on land; a water-breather is con- 
verted into an air-breather; a vegetable feeder into a carnivorous 
animal: yet the series of transmutations are limited to the nature 
of the species and produce no other. The frogs that croak in our 
marshes are as strictly batrachian as those that leapt in Pharaoh’s 
chamber; their metamorphoses have led to nothing higher than their 
original condition, as far as history gives us any knowledge of it. 
With each successive generation the series of changes recommences 
from the old point, and ends in a condition of the animal adapted to 
set the same series again on foot. 
Having traced the principal stages in the metamorphosis of an 
animal from a swimmer toa leaper ; the Lecturer next took an instance 
