Page:Popular Science Monthly Volume 59.djvu/79

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69
THE FROG AS PARENT.

In most such cases the peculiar habit of the parent seems to be associated with an unusual character and development of the eggs. In the common species that have many small eggs, these are left by the parent to develop slowly in the water, where they gradually assume a froglike character. Whereas species having few and large eggs protect these in some manner until they rapidly turn into frogs with little or none of the aquatic youth we are so used to regard as a sine qua non for a frog.

We need go no further than the island of Jamaica for examples of the protected eggs. For there, where everything has to compete strenuously for light and air, the trees themselves support dense populations of plants and these harbor animals of various sorts—amongst them, frogs. One kind of frog in Jamaica lays its eggs in the water that accumulates at the bases of the leaves of Bromelias growing high up on tree trunks, and here the tadpoles have their brief existence.

PSM V59 D079 Frog horns through shell for breathing.png
Fig. 1. Fig. 2.

Another frog abandons even this semblance of aquatic life, laying a few very large eggs under stones and 'trash' on the ground, where they may even be many miles distant from the water—and the young develop into small frogs that hatch from the egg without having known what it is to be a tadpole. Stevenson's fable admits of literal application here.

'Be ashamed of yourself,' said the frog. 'When I was a tadpole I had no tail.' 'Just what I thought,' said the tadpole; 'you never were a tadpole.'

In this frog, however, there is within the egg a stage when the young is active and has a tadpole form, lacking chiefly the medium in which to express its tadpole possibilities. Not being able to swim with its tail, it yet puts this to good use, for it is richly supplied with blood vessels and can serve as a breathing organ.

In the Solomon Islands there is another frog (Rana opisthodon) which lays large eggs, 6-10 nun. thick, on moist ground and not in