Reproduction by Means of Eggs
It might be thought there existed a missing link between animals which lay eggs and those which do not; this, however, is done away with in many instances—one, for example, is found in our commonest indigenous snake. The ringed snake lays eggs which require three weeks time to develop; but when it is kept in captivity, and no sand is strewn in the cage, it does not lay eggs, but retains them until the young ones are developed. This only shows how powerfully influences affect the habit of animals.