THE GEELONG NATURALIST. © 35 
spawn and swims merrily about. It commences to feed greedily: 
on whatever small waterweeds it comes across, and ‘its tail 
becomes large and well adapted for swimming. While very 
young it has a powerful sucker on the under surface of the 
head; by its means it can fasten itself to the under side of 
logs, &e. 
After about a month or so, small protuberances may be 
observed at the root of the tail, one on each side. These 
gradually continue to increase in length, and in about another 
month they finally assume the appearance of full grown limbs, 
with proper joints and toes. Shortly afterwards the fore-limbs 
make their appearance, and about the same time the lungs begin 
to come into use, and the gills gradually leave off working, 
though for some time the animal can use either lungs or gills, 
we find that towards the end of the third month the gills are 
entirely superseded, and the lungs perform the whole work of 
respiration. Marshall’s deseription of this change is so vivid 
that I shall copy it :— 
* When the tadpole is nearly three months old, a distinct 
metamorphosis occurs, whereby the tadpole becomes transformed 
from the fish-like condition in which it has hitherto remained, to 
the purely air breathing stage characteristic of the adult. The tad- 
pole ceases to feed, a casting of the outer layer of the skin takes 
place; the gills are gradually absorbed; the horny jaws are 
thrown off; the large frilled lips shrink up, the mouth loses its 
rounded suctorial form and becomes much wider; the tongue, 
previously small, increases in size; the eyes become larger and 
more prominent; the fore-limbs appear. The left one being 
pushed through the spout-like opening of the branchial chamber, 
the right one forcing its way through the opercular fold, in which 
it leaves aragged hole; the abdomen shrinks; the stomach and 
liver enlarge, but the intestine becomes considerably shorter than 
before and of smaller diameter. The animal. previously a 
vegetable feeder now becomes carnivorous; the gill-clefts and 
close up and important modifications accompanying the change in 
breathing occur in the blood vessels. The tail which is still of 
great length, now begins to shorten and is soon completely 
absorbed. The hind legs lengthen considerably and the animal 
leaves the water as a frog.” d 
It is necessary to remember that the young tadpole has a 
system of circulation exactly like a fish. The venus blood enters 
the sinus venosus, thence into an auricular chamber, from whence 
it passes into the ventricle and is expelled through the Truncus 
arteriosus to the different portions of the body. This is exactly 
what we find in-the fish, namely a complete system of cir- 
` culation with one auricle and one. ventricle,» ‚We: must 
