REPORT ON THE SIPHONOPHOR^E. 121 



curved downwards. Their blind ends are directed towards the ventro-basal angles of the 

 lateral faces. 



Siphon (figs. 13, 14, s). — The single polypite occupies originally the dorsal half of 

 the bracteal cavity (fig. 13), but, when two gonophores are developed, it becomes placed 

 between them more ventrally (fig. 14). Its thick-walled basigaster (sb) is nearly spherical. 

 The spindle-shaped stomach (sm) bears eight yellow hepatic stripes. The contractile 

 proboscis (sr) opens by an octolobate mouth (ss). 



Tentacle (figs. 13, 14,/). — The single tentacle exhibits the same structure, which is 

 accurately described in the case of Calpe pentagona by Kolliker, Leuckart, and others. 

 It arises from the short pedicle of the siphon, between the basigaster and phyllocyst. It 

 bears numerous tentilla, each with a reniform cnidosac and a long terminal filament 

 coiled up spirally in fig. 19. Fig. 20 exhibits its elastic band expanded. 



Gonophores (fig. 13,/; fig. 14, hf). — The bracteal cavity contains sometimes a single 

 gonophore (fig. 13), at other times two or even three gonophores associated, besides some 

 buds of vicarious function. Fig. 14 exhibits a well-developed monoclinic Eudoxia, with a 

 male (h) and a female (f) gonophore. The sexual manubria of both are club-shaped, 

 and fill about the half of the subumbrellar cavity. The umbrella is in both sexes of the 

 same form, distinctly bdateral, with four paired denticulate edges, prolonged at the basal 

 ostium into four strong triangular pyramidal teeth. The two dorsal teeth are much 

 larger than the two ventral. The apex of the umbrella is a curved horn, and contains 

 the pedicular canal ; this gives off at the apex of the subumbrella the four radial 

 canals, as usual. 



Family V. Ees^id^, Haeckel, 1888. 



Erseeidx, Hkl., System der Siphonophoren, 95, p. 33. 



Definition. — Calyconectae monogastricae, representing a single cormidium, which is 

 composed originally of three persons ; a sterile medusome (siphon with tentacle and 

 bract), a sterile special nectophore (without manubrium), and a fertile medusiform 

 gonophore (male or female). 



The family Ersaeidse comprises those monogastric Calyconectae which differ from 

 the preceding Eudoxidse in the possession of a so-called " special nectophore." Their 

 cormidium is therefore composed not of two, but of three, medusomes or persons of the 

 morphological value of a Medusa. The Ersseidse, as independent forms, occur much 

 more rarely than the Eudoxidse. I have observed two genera only, both rather rare, 

 Erssea and Lilsea. 



The sterde medusome of the Ersseidse is composed (as in the Eudoxidse) of three 

 organs — viz.,bract(umbrella), siphon (manubrium), and tentacle (cnido-filament) ; all three 



(zool. chall. exp. — part lxxvii. — 1888.) Hhhh 16 



