REPORT ON THE SIPHONOPHORiE. 117 



an older free Eudoxia). — The hydrophyllium or bract has a diameter of 10 to 1 2 mm., and 

 a sphenoidal or wedge-shaped, rather complicated form, which is best understood if we 

 imagine the true axis of the umbrella standing vertically, its upper or apical pole marked 

 by the top, the lower or basal pole by the centre of the aperture of the cavity. The 

 latter (or the original ostium subumbrellae) is surrounded by five prominent points, an 

 odd dorsal basal point (v 8 ) and four paired lateral ; two of these are dorso-lateral basal 

 points (u G right, u 7 left), the two others ventro-lateral basal points (u* right, u 5 left). 



The opposite apical or superior part of the ripe bract (fig. 14) has the form of a house- 

 roof or of a triangular prism, inclined ventrally. The apical crest (nk) is strongly inclined 

 towards the ventral side, so that the dorsal apical point (u 12 ) may be regarded as the 

 original apex of the bilateral umbrella. The opposite ventral apical point (u 1 ), on the 

 contrary, marks the upper pole of the curved axis of the phyllocyst (be). 



The ventral face of the bract is pentagonal and marked by five prominent points, one 

 odd and four paired. The odd is the above-mentioned ventral apical point (u 1 ). The 

 upper pair of points are the ventro-lateral apical (« 2 right, u* left); the lower pair of 

 points are the ventro-lateral basal points (u* right, u B left). 



The dorsal face of the bract is quadrangular in the upper part, crest-shaped in the 

 lower part, and is marked by five points, three odd and two paired. The uppermost is 

 the odd dorsal apical point (u V2 ), the lowermost the odd dorsal basal point (u 8 ), the 

 hindermost (between the former) the odd dorsal caudal point (u 9 ). At the right side 

 (?( 10 ) and left side (u 11 ) the two dorso-lateral points are prominent. The wedge-shaped 

 dorsal crest (ng) is in the ripe bract (fig. 14) opposite and parallel to the apical crest (nil). 

 All crests and edges of the bract are elegantly denticulated. 



The mature bract of the free Eudoxia (fig. 14) differs from the young bract of the 

 sessile Eudoxoma (fig. 13) mainly in the development of a pair of arched prominent 

 transverse ridges or girdle-wings (u 2 , u 10 , right ; u 3 , u n , left). These separate 

 more distinctly the thicker apical half of the hydrophyllium from its thinner ventral 

 half. An accurate comparison of fig. 13 (young) and fig. 14 (adult) will explain the other 

 differences of these two forms, which are produced by further growth. 



Bracteal Cavity (figs. 13, 14, bh, seen from the right side). — The subumbrellar cavity 

 has the form of a helmet or a Phrygian cap ; it is campanulate, with strongly curved 

 axis, concave at the ventral, convex at the dorsal side. The cavity occupies in the young 

 bract (fig. 13) about two-thirds of the whole body; in the adult (fig. 14) only the basal 

 half. Its basal aperture, or the original mouth of the umbrella, is armed with five large 

 triangular, pyramidal points or teeth, one odd and four paired ; the posterior odd tooth 

 (u s ) is the dorsal basal point ; the two ventro-lateral basal teeth (w 4 , u s ) are larger 

 and wider apart than the two dorso-lateral basal teeth (u fi , u 7 ). A deep ventral 

 groove, through which passes the stem of the cormus (fig. 13, a), is placed in the sagittal 

 plane of the bract, immediately to the ventral side of the subumbrellar cavity (bh). 



