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#Papilloma.# The common wart or verruca is an outgrowth of the surface epidermis. It may be sessile or pedunculated hard or soft. The surface may be smooth, or fissured and foliated like a cauliflower, or it may be divided up into a number of spines. Warts are met with chiefly on the hands, and are often multiple, occurring in clusters or in successive crops.
The cones are about three or four inches long, and two and a half wide, growing in close, sessile clusters among the leaves. The species attains its noblest form in filled-up lake basins, especially in those of the older yosemites, and as we have seen, so prominent a part does it form of their groves that it may well be called the Yosemite Pine.
You have probably noticed that the vertebrate differs greatly from all his predecessors. The gulf between him and them is indeed wide and deep. His origin and ancestry are yet far from certain. But an attempt to decipher his past history, though it may lead to no sure conclusions, will yet be of use to us. Practically all aquatic vertebrates lead a swimming life, neither sessile nor creeping.
But we have not yet seen the worst results of this waste of our highest powers. The sessile animal, which lives mainly for digestion, does not attain as good digestive organs as his more active neighbor, who subordinates digestion to muscle. Lower powers reach their highest development only in proportion as they are strictly subordinated to higher. This may be called a law of biology.
It loses most of its muscles and the larger part of its nervous system; and even the digestive system, which it has made the goal of its existence, is inferior to that of its locomotive ancestors and relatives. But to the vertebrate these lowest depths of stagnation and degeneration are, as a rule, impossible. From true fish upward parasitism and sessile life are practically impossible.
Erasmus Darwin long since pointed out, they do sometimes approach nearly to what may be called travelling; a man of consistent character will never look at a bough, a root, or a tendril without regarding it as a melancholy and unprincipled compromise. On the other hand, many animals are sessile, and some singularly successful genera, as spiders, are in the main liers-in-wait.
Their number is legion, yet how infinite must be the fine floating life, so fine that we cannot note that it clouds the limpid water, on which these sessile gray creatures feed.
Flowers about 2½ inches across, produced abundantly in August; rays narrow and pointed, cupped, with the ends turning outward; leaves lanceolate and sessile; rootstock creeping, forming tuberous thickenings at the base of the stems, which Asa Gray tells us were "the Indian potato of the Assiniboine tribe," mentioned by Douglas, who called the plant H. tuberosus. H. maximiliani.
This was a sore trouble to me, adding as I thought one more instance of the abrupt appearance of a great group of species. But my work had hardly been published, when a skilful palaeontologist, M. Bosquet, sent me a drawing of a perfect specimen of an unmistakeable sessile cirripede, which he had himself extracted from the chalk of Belgium.
The Balanidae or sessile cirripedes, on the other hand, have no ovigerous frena, the eggs lying loose at the bottom of the sack, within the well-enclosed shell; but they have, in the same relative position with the frena, large, much-folded membranes, which freely communicate with the circulatory lacunae of the sack and body, and which have been considered by all naturalists to act as branchiae.
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