REPORT ON THE SIPHONOPHOR^E. 135 



broader in the upper than in the lower half. It occupies the two distal thirds of the 

 nectophore, whilst its proximal third is taken by the soinatocyst (cs). Its ventral side is 

 separated by a thin frontal septum from the adjacent hydrcecium. The basal mouth of the 

 nectosac is obliquely truncate and surrounded by five strong triangular teeth, the distal 

 ends of the five exumbrellar crests. The two ventral teeth (as the terminal lobes of the 

 two hydrcecial plates) are about four times as large as the three other teeth, which 

 form an odd dorsal point and two paired lateral points. 



Canals of the Nectosac. — The nectocalycine duct, which arises from the top of the 

 stem (aa), descends nearly to the middle of the dorsal median line of the subumbrella, 

 and divides here into four radial canals, two odd and two paired. The odd ventral canal 

 (cv) is the shortest, and descends immediately straight to the ostium of the nectosac. 

 The odd dorsal canal (cd) is the longest ; it ascends, in the dorsal median line, to the 

 apical top of the nectosac, and then descends downwards along its whole ventral median 

 line. The two paired lateral canals (right ex, and left cl) are intermediate in length 

 between the former and the latter, and have a strongly bent course. They run firstly 

 ascending towards the dorsal side, form in the upper half of the nectosac a nearly circular 

 loop, and then are turned ventrally and downwards. The four radial canals are united 

 at the ostium of the nectosac by a circular canal, which embraces the velum (v). 



Hydrcecium (figs. 1-4, «»). — The funnel-cavity of the nectophore, into which the 

 contracted siphosome may be partly retracted, is a long, nearly cylindrical and slightly 

 bent canal, which occupies the two distal thirds of the ventral half of the umbrella. It 

 is separated from the dorsally adjacent nectosac by a thin frontal septum, and incom- 

 pletely closed on its ventral side by the two triangular ventral wings of the exumbrella 

 overlapping one another (figs. 3, 4, nx right, nl left). Its basal ostium is protected at 

 the dorsal side by the two terminal lobes of the ventral crest. The apex of the hydrcecial 

 canal touches the base of the somatocyst. 



Somatocyst (cs). — The axial canal of the tubular stem is prolonged above its apex 

 into a pyriform cavity, nearly filled up by large vacuolated entoderm-cells. This is the 

 pyriform somatocyst, which encloses in its dilated uppermost part a hydrostatic oil- 

 globule (co). It occupies the uppermost or apical third of the nectophore, and is far 

 prominent over the top of the nectosac. It is twice as long as broad, and nearly one- 

 third as long as the nectophore. 



Siphosome. — The common tubular stem, which arises in the closed apex of the 

 hydrcecium, at the base of the somatocyst, proceeds through the basal ostium of the 

 former to a considerable length. It is beset by a series of numerous buds in the upper 

 part, and eight to twelve fully-developed cormidia in the lower part. These are 

 alternating male and female, separated by equal free internodes (fig. 1). 



Cormidia (figs. 6, 7). — Each cormidium, or " group of individuals," is a eudoxome, 

 composed of two medusomes, a sterile and a fertile. The sterile Medusa exhibits a 



