Tha American S^ongilh. 113 



does the vesicle appear to contract suddenly; whereas by watching 

 it through a complete circuit of diastole and systole, one learns that 

 its function is, on the whole, performed very slowly. This very 

 abrupt movement, quite happily, may serve to rebut any such 

 objection as that the otherv/ise tardy action is merely the result of 

 protoplasmic contraction of the body, as in certain Palmellate 

 Zoospores. Their immovable position, as regards the body contents, 

 is another item of rebutting evidence. 



The Spiculm (Fig. 1, e, e^) are very slender, slightly curved, 

 needle-shaped bodies, gradually tapering to a sharp point at each 

 end. They have a bright amber colour, and a rather dark, strongly 

 refractive outline. From tip to tip they are slightly roughened by 

 irregularly-scattered, low, but acute prominences or knobs. There 

 are two kinds of spicules, large and small, but they differ in no 

 other respect. The larger (e) are from four to six times longer 

 and thicker than the smaller ones. They occur in bundles of two, 

 three, «r four ; and act as props to hold up the outer investing 

 membrane, as described in the early part of this article. They 

 seldom arise perpendicularly from the monadigerous mass, but 

 more or less obliquely ; and, in forming bundles, stand across each 

 other like- stacked arms. We seldom found spicules penetrating the 

 monadigerous mass far beyond the epithelioid, inner investing 

 membrane. They evidently belong, universally, to the investing 

 membrane, and assist it in forming a framework in which the 

 inner mass is suspended. The smaJler spicules (e^) are strictly 

 confined to the outer division {a) of the investing membrane, and 

 lie there on their sides, completely immersed in its thickness. They 

 are scattered irregularly and sparsely about, and frequently cross 

 each other at varying angles. We observe no nearer approach to a 

 methodical arrangement among either the large or the small spicules ; 

 yet their very irregularity, being after a kind, and constant in that 

 kind, may be recognized in some sense as methodical. 



General Considerations. — Seeing the secluded position of the 

 monad-cephalids, deeply ensconced in little chambers below the 

 general surface of the circulatory apartment, it is not directly 

 evident that their jlagella have any agency in keeping up the 

 inflow and outflow of currents through the aflerent and efferent 

 ostioles. Nowhere else are vibrating or non-vibrating ciha or 

 cilia-like bodies to be met with than in the monad chambers. 

 And since the eflerent ostioles are irregularly interspersed among 

 the much more numerous afferent ostioles, we cannot conceive how 

 the flagella in any way could influence currents to move in a 

 particular direction, from the smaller apertures toward the larger 

 ones. They no doubt keep up a direct flow of matter into the 

 sunken chambers, but the current comes from the inner depths of 

 the circulatory apartment, and far away from the ostioles. In this 



