170 THE VOYAGE OF H.M.S. CHALLENGER. 



Desmof)liyes annectens, n. sp. (PI. XXX.). 



Habitat. — Indian Ocean, south coast of Ceylon, December 1881 (Haeckel). 



Nectosome (fig. 1). — The swimming column was composed, in the only specimen 

 observed, of six nectophores arranged in two opposite series. The two uppermost 

 nectophores were half as large as the two lowermost, and the two bells of the second pair 

 placed between them, intermediate in size. Each of the two largest inferior nectopbores 

 had a length of 15 mm. and a breadth of 10 mm., and the entire biserial nectosome was 

 about 30 mm. long and 18 mm. broad. 



Nectophores. — The swimming-bells are on the whole very similar to those of Praya 

 galea, their jelly soft and delicate, the surface smooth and rounded, without edges. The 

 form is obliquely campanulate or mitriform, the apical part rounded, the basal part with 

 the ostium obliquely truncate. 



The dorsal (outer or abaxial) face of each nectophore is convex and smoothly rounded, 

 as is also the lateral face. The ventral face, however (turned to the common axis of 

 the stem), is concave and forms two parallel, longitudinal, prominent wings, which 

 embrace a hemicylindrical groove. The ventral grooves of each two opposite nectophores 

 are so fitted one into another that they form together a cylindrical canal. This axial 

 tube, tapering towards the apex, is the hydrcecial canal, which encloses the superior part 

 of the common stem ; the contracted siphosome may be partly retracted into it. 



Each nectophore is attached to the common stem by means of a short pedicle, a 

 vertical triangular lamella, which arises by a broad base from the upper third of the 

 ventral groove, and is fixed at its apex to the uppermost part of the stem. The pedicle 

 encloses the peduncular canal which connects the stem-cavity with the nectosac. 



Nectosac. — The inferior basal or distal half of each nectophore is occupied by the 

 muscular subumbrella, which has an obliquely campanulate form. Its basal mouth is 

 wide, and surrounded by a broad velum. The four radial canals of the subumbrella are 

 of different lengths, the two lateral canals (right and left) being larger than the ventral 

 (or axial) canal, and smaller than the dorsal (or abaxial) canal. They unite at the base of 

 the velum by a circular marginal canal, and this is beset with eight red pigment spots 

 or ocelli, similar to those in the special nectophores of the cormidia. Four of them are 

 placed perradially (at the distal end of the four radial canals) and four others inter- 

 radially (between the former). There are no rudimentary tentacles on the margin of 

 the umbrella ; these are peculiar to the special nectophores. 



The superior, apical or proximal, half of the nectophore contains two canals which are 

 placed in its sagittal plane. The peduncular canal, which arises from the canal of the 

 common stem in its uppermost part, enters by the triangular pedicle of the nectophore in 

 its jelly-substance, and descends obliquely in a curve towards the apex of the subumbrella, 



