REPORT ON THE SIPHONOPHORiE. 167 



the opening of the nectosac (uo) surrounded by the velum (v), and at its ventral side 

 the opening of the hydrcecia! canal (ui). Near the velum arise two small lateral spines, 

 which lie in the radius of the two much larger triangular teeth, being the distal pro- 

 longations of the two dorso-lateral edges (n l left, iv right). 



Nectosac (figs. 1-4, id 1 ). — The subumbrella of the second nectophore is cylindrical 

 and occupies its dorsal half. The nectocalycine duct, which comes from the top of the 

 stem and enters into the subumbrella somewhat below its apex, divides into the four 

 radial canals (cd dorsal, cv ventral, ex right, cl left). These descend vertically and 

 nearly parallel to the ostium, where they are united by the circular canal. 



Ili/drcccial Canal — The ventral groove of the second nectophore, which forms the 

 continuation of the hydrcecium of the first, has an irregular form (figs. 10-12, ui, in 

 transverse section). It is enclosed between the ventral wall of the second nectophore, 

 and the two broad ventro-lateral wings which arise from it, the right (ux) overlapping 

 somewhat the left (id). 



Siphosome (as). — The long stem, which may be retracted completely into the 

 hydrcecial canal, bears a series of twenty to thirty or more cormidia. These are 

 detached from the stem before they reach sexual maturity and swim freely about as 

 Aglaisma gegenbauri (PI. XL.). They are characterised by a cuboidal bract, which has 

 a caudal prolongation at the inferior dorsal edge, and by four radial canals arising from 

 the phyllocyst (two slender odd sagittal and two paired broad lateral). Compare on then- 

 structure, above p. 119. 



Family VIII. Desmoph yid m, Haeckel, 1888. 

 Desmoph tjidx, HkL, Sj^stem der Siphonophoren, 95, p. 36. 



Definition. — Calyconectse polygastriese, with a biserial nectosome, composed of four 

 to six or more opposite nectophores. Cormidia ordinate, eudoxiform or ersgeiform, 

 separated by equal free internodes ; each siphon with a bract. 



The family DesmophyidaB, represented by two new genera only, is of special interest 

 as a connecting link between the preceding (VII.) and the following family (IX.). It 

 agrees in general structure and composition with the Diphyidfe, but differs from them in 

 the oreater number of nectophores which are arranged in a biserial nectosome. This 

 latter character is also found in the Polyphyidae, which, however, differ in the absence 

 of bracts. The Desmoph yidaj may be derived immediately from the Diphyidse, by 

 multiplication of the nectophores. The Polyphyidee may have arisen from the former 

 by reduction and loss of the bracts. 



Two genera only of Desniophyidee have been observed by me, each with a single 

 species. Both agree in the form of the rounded edgeless nectophores and bracts with the 



