With the exception of a few days, the weather this month has been extremely favourable; indeed, for the greater part, summer-like--a pleasant change from what we have experienced of late. The peculiar white rubber-like folds of ribbon which have been adhering to the Rock surface for the past two months, and which we erroneously supposed to be the ova of some fish, turn out to be the spawn of the slugs I have already described, and with which the Rock has been freely invested of late--proof of which several have been seen in the act of extrusion. These shell-less molluscs have been much in evidence this season; and representatives of three distinct families are to be met with, namely, the Onchidoridæ, Tritoniidæ, and Eolididæ. Cannibals, they attack their own species without compunction, and devour each other’s spawn. Darwin computed that some “ribbons” contained as many as six hundred thousand eggs. The acorn barnacles which have escaped the voracity of the white whelks have in some places attained a height of two inches. On examination, each shelly casement is seen charged with spawn, which, later on, will be liberated as free swimmers, totally unlike the parent form, to enjoy a brief period of unrestricted freedom before settling down on the Rock surface, or, for that matter, any immersed object that comes handy, and ultimately assuming the adult form. The young swimmer, feeling itself gradually becoming invested with a shelly covering, casts about for a suitable site to pass the remainder of its existence. Selecting the Rock surface, it attaches itself by its head, the antennæ become cemented to the surface, the eyes remain in a rudimentary form, the shelly plates which latterly form the door of its domicile appear, a few more pairs of legs are developed, and by a series of frequent moultings (like other crustaceans) arrives at the perfect state. The bunches of “fingers” which we see this animal protrude and withdraw when under water are in reality its feet, of which there are twelve pairs, the rhythmic expansion and contraction of which induce a current in the water attracting to its mouth the minute objects upon which it feeds, thus giving rise to the saying that this animal stands on its head and literally kicks its food into its mouth. In all other crustacea the sexes are distinct, the barnacles alone having the peculiarity of being bi-sexual, or having both sexes united in the same individual. The general tendency throughout nature--the evolution from a lower to a higher order, from the simple to the complex--appears in the case of the barnacle to be reversed. Gifted in the initial stage of its existence with all the functions of a free-swimming animal, and possessing organs which ultimately become rudimentary, the final phase in which all power of volition is lost, certainly does not appear one of progression.