Rose, so far back as 183719; but in the later stages the presence of albuminoid matter made a great difference. Now, after a few days, the calcium carbonate was seen to be deposited in the form of large rounded concretions, with a more or less distinct central nucleus, and with a surrounding structure at once radiate and {422} concentric; the presence of concentric zones or lamellae, alternately dark and clear, was especially charôÙacôÙterôÙisôÙtic. These round ãcalôÙcoôÙspheôÙritesã shewed a tendency to aggregate together
in layers, and then to assume polyhedral, or often regularly hexagonal, outlines. In this latter condition they closely resemble
the