REPORT ON THE SIPHONOPHOR^E. 305 



Order V. CYSTONECTAE, Haeckel, 1888. 

 (Pis. XXII.-XXVI.) 



Pneumatqphoridx, Chun, 1882, 86, p. 1168. 

 Cystonectse, Haeckel, 1888, 95, p. 44. 



Definition. — Siphonophorse with a large apical pneumatophore, without nectophores 

 and without bracts. Nectosome represented only by the pneumatophore, which always 

 bears an apical stigma. Siphosome either a single cormidium with one siphon 

 (Monogastricse), or a tubular or vesicular trunk which bears numerous cormidia 

 (Polygastricae) Gonodendra always monostylic, provided with gonopalpons. 



The order Cystonectae comprises all Siphonanthae which possess neither nectophores 

 nor bracts, the only organ of swimming being the large apical pneumatophore. They 

 differ in this respect from the three preceding orders, and agree with the Disconanthae or 

 Disconectae ; but the structure of the float, as well as the entire organisation, is in 

 these latter perfectly different (compare above, pp. 25, 26). We unite in the order 

 Cystonectse five different families, three of which are new, viz., the monogastric Cystalidse 

 and the polygastric Epibulidse and Salacidas ; the two other families, formerly known, and 

 both polygastric, are the Rhizophysidse (usually united with the Physonectae) and the 

 Physalidae ; these two families have been united by Chun, in 1882, under the name 

 Pneumatophoridae (86, p. 1168). All known Cystonectse agree in the complete 

 absence of nectophores and bracts, and in the possession of a large pneumatophore of 

 peculiar structure, provided constantly with an apical stigma for the emission of air. 

 All the genera of this order agree further in the peculiar composition of the monostylic 

 gonodendra, the gynophores of which are detached from the trunk before ripening. In 

 most other respects the Cystonectse agree generally with the Physonectae ; they may be 

 derived from this order by the loss of the nectophores. 



History. — Eschscholtz in his fundamental work (1) described, in 1829, three genera 

 and six species of Siphonophorse which belong to our order Cystonectae, viz., (1) the 

 Mediterranean Rhizophysa jiliformis, Lamk. (described already in 1775 by Forskal, 11, 

 as Physophora Jiliformis), and the closely allied Rhizophysa planostoma, Peron (14, pi. 

 xxix. fig. 3) ; (2) the Australian Epibulia chamissonis (figured in 1821 by Eysenhardt, 

 77, as Rhizophysa chamissonis); and (3) the well-known interesting genus Physalia with 

 three species (the Atlantic Physalia caravella, the Indian Physalia pelagica, and 

 the Pacific Physalia utriculus). Eschscholtz, as well as most following authors, united 

 these three genera of Cystonectae with the Physophoridae (our Physonectae). 



Brandt, in 1835, relying on the excellent (unfortunately hitherto unpublished) figures 

 and descriptions of several new Cystonectae by Mertens, established for them two different 



(ZOOL. CHALL. EXP. PART LXXVII. — 1888.) Hhhh 39 



