COME FROM THE EGG

Greymouth Evening Star, 10 August 1933, Page 8

COME FROM THE EGG

ANIMALS’ WIDE RANGE All birds come from eggs, but not all eggs from birds. The eggs of birds are generally attractive objects, which cannot be said of all eggs. The size of an egg is by no means always a guide to the size of the bird that produced it. The common gull lays a larger egg than the pheasant, and the kiwi, a New Zealand species, scarcely as big as an ordinary fowl, j lays an egg little inferior in size to that of an emu —in fact, the largest egg known relatively to the bulk of the bird, as the cuckoo’s is the smallest (says a writer in the “Manchester Guardian”). Of birds living at the present day the ostrich lays by far the biggest egg, yet even this is dwarfed by the enormous egg of aepyornis, an ostrich-like bird, twelve

feet high, that once lived in Madagascar but is now extinct. This egg had a capacity of about two gallons. At the other end of the scale are the minute eggs of humming-birds, weighing only a few grains. Often the young bird that issues from a large* egg is in a well-grown condition when, hatched, and able to look after itself.', tolerably well, whereas the tenants) of smaller eggs emerge blind, pathetically helpless, and dependant for a considerable time upon parential solicitude. In the average case incubating, is not far advanced when an egg is j laid and is checked when it becomes j cold, to be resumed under the in- 1 fluence of warmth derived through' one of the parents, or both in turn, “sitting” on it, a duty that must he, religiously observed for a prolonged j period. CROCODILES THAT CRY I Reptiles in the main reproduce < through the medium of eggs, and as a rule a considerable number are

laid at a time. Generally they are of a whitish colour, not spotted as in nine out of ten species of birds, and the shell may be either membranous or chalky and brittle. Crocodiles lay from twenty to sixty oval eggs, approximating in size to those of a goose. They are buried in the sand, and the parent is thought to assist in incubation. At any rate , the young are helped to escape from the sand when the shells break, the mother being apprised of the right moment by a peculiar noise, said to resemble crying, emitted by the infant crocodiles.

Tortoises lay round eggs not unlike those of some birds of prey. Turtles come ashore for breeding purposes and deposit their eggs in the sand. The green turtle digs a hole with its flippers and fills it with eggs to the number of 150 or more, smoothing them over with sand, the heat-retain-ing property of which suffices to hatch them.

Snakes lay numerous eggs, which often adhere together by means of a viscid substance. Sometimes the heat of the sun alone serves to hatch them, but development is often hastened by their being placed in decaying vegetable matter or manure. Pythons incubate them, and somereptiles arc viviparous—that is, the eggs are hatched while still within the body. Such is also the case with certain aquatic snakes, the British viviparous lizard, and a bish known as the viviparous blenny, which produces as many as fifty young at a birth.

FROGS The eggs of amphibians resemble those of fishes and are laid in water singly, in strings, or in compact masses. A familiar example is the spawn of the common frog, which is found floating in ponds or dikes. Each of the numerous eggs is surrounded by a coating of albumen, which swells up in contact with the water to produce a. compact, jelly-like mass, partly

nutritive and partly protective, among which the developing embryos (tadpoles) are conspicuous as black lots that eventually uncurl and swim free of the entangling jelly. The adult frog results, as every schoolboy knows, through gradual metamorphosis of the tadpole, but in the Solomon Islands there is a landfrog laying eggs as large as marbles, from wvhich issue fully-developed frogs, a most unusual condition among amphibia. Another striking exception is the Surinam toad, whose eggs are placed by the male upon the back of tlie female, where each becomes embedded in a sort of pouch from which emerge later miniature but complete frogs.

There are even egg-laying mammals —the spiny ant-eater and the duckbilled platypus of Australia. Both creatures arc unquestionably mammals, though of somewhat lowly organisation, and yet they lay eggs. Fishes as a class are extraordinarily prolific, and their eggs are usually minute. It has been computed that the roe of a herring may contain 50,000 eggs, and that of a turbot more than 14,000,000.