These were
arranged two deep in transverse rows forming a ribbon. The ribbon
adhered by its edge to the rock in an oval spire. One which I found
measured nearly twenty inches in length and half in breadth. By
counting how many balls were contained in a tenth of an inch in the
row, and how many rows in an equal length of the ribbon, on the
most moderate computation there were six hundred thousand eggs. Yet
this Doris was certainly not very common: although I was often
searching under the stones, I saw only seven individuals. NO
FALLACY IS MORE COMMON WITH NATURALISTS, THAN THAT THE NUMBERS OF
AN INDIVIDUAL SPECIES DEPEND ON ITS POWERS OF PROPAGATION.) I will
mention only one class of facts, relating to certain zoophytes in
the more highly organised division of that class. Several genera
(Flustra, Eschara, Cellaria, Crisia, and others) agree in having
singular movable organs (like those of Flustra avicularia, found in
the European seas) attached to their cells. The organ, in the
greater number of cases, very closely resembles the head of a
vulture; but the lower mandible can be opened much wider than in a
real bird's beak. The head itself possesses considerable powers of
movement, by means of a short neck.
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