The Excrescence, as described at No. 3, arises through the development of areolar tissue out of a transparent amply nucleated blastema. In its cavity are lodged, sometimes in vast quantities, simple and laminated, semi-opaque, incrusted growths, from the size of an elementary granule to a diameter of 1/ 25th of a millimetre, the circumference, most common to incrusted cysts.

The excrescence simultaneously becomes fibrous, and shrivels, with condensation of fibrous parts, into the solid masses above described.

In these observations, two phenomena engross our attention, namely, the development of the secondary cyst and the hollow growths forming upon the internal wall of the cyst. We have made them the subject of an extended investigation, with a view to the solution of the double question as to the nature of elementary germ for cysts, both primary and secondary, and of its ulterior development, - and as to the import of the said hollow growths.

(a.) The cysts best adapted for the inquiry, are young, small, clustered cysts, just visible to the naked eye; others being probably present, still smaller, clown to the germ itself, out of which they spring. The cysts so frequent in the kidneys, or on the broad ligaments, and on the peritoneum of the tubes and ovaries, furnish ample materials for the purpose.