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Show 400 UTRICULARIA NEGLECTA.. bHAP. XVII. bladder as shown in the longitudinal section (fig. 20) of the c~llar and valve; it is also shown at c, in fig. 18. The edge of the valve can thus open only inwards. As both the valve and collar dip into the bladder, a hollow or depression is here formed, at the base of which lies the slit-like orifice. . The valve is colourless, highly transparent, flexible and elastic. It is convex in a transverse direction, but has been drawn (fig. 19) in a flattened state, by which its apparent breadth is increased. It is fonned, FIG. 20. ( nricularia neglecta.) Longitudinal vertical section through the ventral portion of a bladd0r; showing valve and collar. v, valve; the whole projection above c forms the eollar; b, bifid processes; s, ventral surface of bladder. according to Cohn, of two layers of small cells, which are continuous with the two layers of larger cells forming the walls of the bladder, of which it is evidently a prolongation. Two pairs of transparent pointed bristles, about as long as the valve itself, arise from near the free posterior margin (fig. 18), and point o bliq uel y outwards in the direction of the antennce. There are also on the surface of the valve numerous glands, as I will call them; for they have the power of absorption, though I doubt whether they ever secrete. They consist of three kinds, which CHAP. XVII. S'rRUCTURE OF THE BLADDER. 401 to a certain extent graduate into one another. Those situa~ed ~·ound the anterior margin of the valve (upper margin ln fig. 19) are very numerous and crowded. tog·~ther ; they co:nsist of an oblong head on a long pedicel. The pedicel itself is formed of an elonD"ated cell, surmounted by a short one. The glands to~ards the free posterior margin are much larger, few in nuinber, ~nd almost spherical, having short footstalks; the head Is formed by the con:fl uence of two cells the lower one answering to the short upper cell o/ the pe~icel. of the oblong glands. The glands of the thud kind have transversely elongated heads, and are seated on very short footstalks; so that they stand parallel and ·close to the surface of the valve ; they may be called the two-armed glands. The cells forming all these glands contain a nucleus, and are lined by a thin layer of more or less granular protoplasm the primordial utricle of Mohl. They are filled with fluid, which must hold much matter in solution judging from the quantity coagulated after they hav~ b.een .long ~mmersed in alcohol or ether. The depression In which the valve lies is also lined with innumm ·able glands; those at the sides having oblong heads and elongated pedicels, exactly like the glands on the adjoining parts of the valve. The collar (called the peristorne by Cohn) is evidently formed, like the valve, by an inward projection of the walls of the bladder. The cells composing the outer surface, or that facing the valve, have rather thick walls, are of a brownish colour, minute, very ~umerous, and elongated; the lower ones being divided Into two by vertical partitions. The whole presents a coin~lex and elegant appearance. The cells forming the Inner surface are continuous with those over the whole inner surface of the bladder. The space be- 2 D |
