The Cambridge natural history, Vol. 08 (of 10)Gadow, Hans
Science
The Cambridge natural history, Vol. 08 (of 10)
Gadow, Hans
Animals
In the case of old females which have produced offspring before, the whole
process is more complicated. The sperma, taken up in July, remains in the
receptaculum of the cloaca until the May or June following, _i.e._ until
the previous larvae have passed out of the uterus and are born. Then the
spermatozoa ascend to the upper ends of the oviducts, where they meet and
fertilise the new eggs. After these have descended into and filled the
uterus, and are already developing into embryos, copulation takes place
again in July, preparatory for next year's eggs.
The new-born salamanders have three pairs of long external gills, a long
tail furnished with a broad dorsal and ventral fin, and four limbs,
although these are small. The total length is about 25 mm. or 1 inch. The
general colour is blackish with a pretty metallic golden and greenish
lustre. The little creatures are very active, and at once eat living or
dead animal matter. In captivity they are liable to nibble each other's
gills and tails. During the first six or eight weeks they assume a row of
dark spots on the sides; these spots enlarge, and the whole skin becomes
darker. Yellow spots appear next, first above the eyes and on the thighs,
later upon the back; the ground-colour at the same time becomes black,
until at the beginning of the fourth month they look like the parents.
The metamorphosis is very gradual. The tail-fin diminishes first, but the
gills grow until shortly before the little creatures leave the water.
Darkness, cold, and insufficient food retard the metamorphosis, sometimes
until October. It is easy to rear them artificially provided they are well
fed, kept in a light place, and in clean, well aerated water. If prevented
from leaving the latter, for instance when kept in a glass vessel with
vertical walls, or if hindered by a piece of gauze from rising to the
surface and taking in air, they can be kept as larvae well into the winter.
Very young, perfect little salamanders, of from 1 to 2 inches in length,
are excessively rare; even specimens of 3 inches are far from common. They
probably spend the first two or three years of their life in careful
seclusion.
A few adults can be easily kept for many years in shady {119}places
provided with moss, rotten stumps and stones, to afford them suitable moist
and cool hiding-places, and they readily take earthworms, larvae of
beetles, snails, woodlice, etc. But any attempt to keep them in large
numbers ends in failure. They congregate together in clumps, all making for
the same cavity or recess, as if that were the only one in existence (very
likely they are right in so far as that place is probably the best), and
they get rapidly enlarging sores, chiefly on the elbows and knees. These
are soon infested with fungoid growths, and this disease spreads like an
epidemic and soon carries them off.
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