COME FROM THE EGG

Evening Star, Issue 21504, 31 August 1933, Page 1

COME FROM THE EGG

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, arid the kiwi, a New Zealand species, scarcely as big as an ordinary fowl, 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 ‘ Alanchester 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 12ft high _ that once lived in Aladagascar, but. is now extinct. The 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 wellgrown condition when hatched, and able to look after itself tolerably well, whereas the tenants of smaller eggs emerge blind, pathetically helpless, and dependent for a considerable time upon parental solicitude. In the average case incubating is not far_ advanced when an egg is laid, and is checked when it becomes cold, to be resumed under the influence of warmth derived through one of the parents, or both in turn “ sitting ” on it, a duty that must be religiously observed for a prolonged period. CROCODILES THAT CRY. 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 ashor.e 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-retaining property of which suffices to hatch them. Snakes lay numerous eggs, which often adhere" together by means of a viscid substaneg. Sometimes the heat oi vthe sh-A alonfe" ’servesi do-hatch:.them,, but development is often hastened, by their being placed in decaying vegetable matter or manure. Pythons incubate them, and some reptiles are viviparous —that is, the eggs are hatched while still within the body. Such is also the ease with certain aquatic snakes, the British viviparous lizard and a fish 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 dykes. 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 dots 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 land frog laying eggs as large as marbles, from which 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 the 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 are 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.