The records of Australian biology bear sufficient witness to the fact that it is extremely difficult, even for residents in Australia, to procure the material necessary for an investigation into the development of the egg of Ornithorhynchus. It is only through the organisation of special expeditions, with ample resources both of time and money, that any large measure of success in this direction can be hoped for. The animal itself, though pretty widely distributed, and probably still far from becoming extinct, is to he found, in any one locality, only in comparatively small numbers. It is now much less plentiful than formerly, owing to the demand for its fur—a demand which is still satisfied in spite of the measure of legal protection which the animal has obtained in the various Australian States. The depredations of the fur-hunter are not easily repaired, since the animal breeds only once in the year and produces but two eggs at a time.