Chap. VII. EUCOPE DIAPHANA. 323 



gradually thins out laterally, as may be seen in an oblique view {Fig. 2, e^), until 

 at right angles to the plane of greatest thickening the two opposite sides are alike 

 {Fig. 6, e, e). From the latter point of view, the outline is elongate pear-shaped, 

 whereas on the thickest side {Fig. 5, e^) the contour is arched inwardly, and on the 

 side opposite to this {e) the outline is an outward curve. Just below the con- 

 striction {Fig. 5, /) of each joint, and immediately above the point of greatest 

 thickening (e), the pedicels arise, at an average angle, to the main stem, of about 

 thirty or thirty-five degrees. 



The diversion of the chyraiferous tube from the main stem begins exactly 

 where the corneous tube is thickest, and, as it were, rests upon this point, the 

 thickening, therefore, forming a part of the pedicel, yet thinning out so rapidly 

 that the second ring is not affected by it, but has an equal thickness on all 

 sides ; and so is it with the rest of the pedicel up to the base of the calycle, 

 while, at the same time, the calibre gradually lessens, and the rings become 

 successively thinner. The number of rings varies from eight to twelve, but usually 

 there are not more than five to eight, the higher number apparently arising from 

 an injury and the renewal of the lost part; in which case, as often happens among 

 Hydroids, the tendency is to a distortion in form, or an exaggeration in number. 

 The calycle {a, a^) has the form of a cup, whose sides diverge at an angle of 

 thirty or thirty-five degrees, and whose depth is to its greatest breadth as six is to 

 five. The margin, which is perfectly smooth, is slightly oblique to the axis of 

 the pedicel, the slant trending toward the stem, and, consequently, the outline, as 

 seen from above {Fig. S"), is broadly ovate. The wall of the calycle {Fig. 5, a, a^) 

 is much thicker than that of the pedicel, and even varies on different sides ; on 

 the side furthest from the main stem, and directly above the great thickening in 

 the joints of the latter, the wall is twice as thick {a^) as that of the pedicel, 

 but passing around to the opposite side {a) it gradually diminishes to half this 

 amount. At the margin the wall thins out to a sharp edge rather suddenly, and 

 with like rapidity the base diminishes as it passes into the pedicel. The trans- 

 verse perforated septum {Figs. 5 and 7, k), which projects into the inferior part 

 of the cavity of the calycle, is also very thick, and, in a transverse section, has 

 the form of an isosceles triangle, one of whose longer sides (/) rests against the 

 inner face of the calycle, while the other long side, which is free, faces obliquely 

 toward the mouth of the cup, and the short side, also free, trends at right angles 

 to the last, and faces obliquely toward the base of the calycle. The median third 

 of the partition is occupied by an aperture, formed by the very abrupt termination 

 of the edge. From the lower margin of the truncate edge there hangs a very 

 thin and transparent tube {m), with an irregular opening {n) at the lower end. 

 This tube is, perhaps, one third longer than its transverse diameter, but owing to 



