AMPHIBIAN AND INVERTEBRATE DEVELOPMENT 65
embryonic development is in some degree comparable with the RNA
content (Urbani, 1954; Urbani and De Cesaris Coromaldi, 1954a).
Once embryonic development is complete, the larva starts feeding in
preparation for metamorphosis, which presents more complex phenomena in the Anura than in the Urodeles.
Recently, BafFoni (1960) carefully investigated the morphological
events of metamorphosis, and we refer the interested reader to his work
for an exhaustive treatment of the subject, while for our part we shall
mention only the facts which are closely related to the scope of our
survey.
After reaching an average weight of about 150 mg, the larva of Bufo
vulgaris loses weight through dehydration and the concurrent utilization
of materials (Adolph, 1931; Davenport, 1897; HelfF, 1926; Needham,
1942; Schaper, 1902; Urbani, 1957).
At this time the animal stops feeding and reverts to the 'closed box'
condition characteristic of the embryonic stage, the necessary energy
being drawn from the reserve materials and from the protoplasm itself.
Reductions in fresh and dry weight during metamorphosis are shown in
Fig. 2; the data were obtained at the following stages: I—larva at the
Bufo vulgaris
Water content in %
Wet weight in %
Dry weight in mg
mg
-110
Stages
I
IH
IV
t t T *
FIG. 2. Changes in water content, fresh weight, and dry weight during metamorphosis
(Urbani, 1957).