REPORT ON THE SIPHONOPHORiE. 



209 



Gonophores. — The rnedusiform gonophores arise in clusters from branched gono- 

 styles, and possess in both sexes of the Apolemiche a well-developed umbrella with four 

 radial canals and a connecting ring-canal ; Dicymba (PI. XVIII. figs. 4, 6) is besides 

 distinguished by the possession of four rudimentary tentacles which are placed at the 

 distal end of the radial canals and bear a red ocellus (as in Desmopliyes and Lilyopsis). 

 The ovarium (or the manubrium of the female Medusa) includes a single large ovule 

 surrounded by an irregular network of spadicine canals (figs. 3, 4). The spermarium (or 

 the manubrium of the male Medusa) is a large club-shaped sac with a central spadix 

 (figs. 5, 6). The corms of Apolemia are dioecious and bear in each cormidium a single 

 gonodendron, all of the same sex in one corm. The corms of Apolemopsis and Dicymba 

 are monoecious and bear in each cormidium two gonodendra, a male and a female ; they 

 arise separately from the common trunk on the base of the cormidium. 



Synopsis of the Genera of Apolemidse. 



I. Subfamily Dictmbidje. 



Nectosome with two opposite neoto- 

 phores only. Cormidia monogastric, 

 each with a single siphon and cyston. 



II. Subfamily Apolemopsim;. 



Nectosome with two opposite rows of 

 nectophores. Cormidia polygastric, 

 each with several siphons and eystons. 



Internodes of the siphosome naked. Corms 

 moncecious. Cormidia monoclinic, with 

 two gonochoristic gonodendra (a male and 

 a female), ...... 39. Dicymba. 



' Internodes of the siphosome naked. Corms 

 dioecious. Cormidia diclinic, with a 

 single gonodendron (either male or female), 40a. Apolemia. 



Internodes of the siphosome covered with 

 bracts. Corms monoecious. Cormidiamono- 

 clinic, with two gonochoristic gonodendra, 40?;. Apolemopsis. 



Genus 39. Dicymba, 1 Haeckel, 1888. 



Dicymba, Hkl., System der Siphonophoren, p. 39. 



Definition. — Apoleroidse with two large opposite nectophores only. Internodes of the 

 siphosome naked. Cormidia monogastric and monoclinic, each with a single siphon and 

 cyston, and with two separate gonodendra, a male and a female. Corms moncecious. 



The genus Dicymba is represented by a new interesting Apolemid, which I 

 observed living during my voyage through the Indian Ocean, from Aden to Bombay, in 

 November 1881. The special organisation of the single parts which compose the 

 polygastric corm, is similar to that of the common Apolemia ; but their disposition and 

 number are different. The nectosome of Dicymba is composed of two large opposite 

 nectophores only (as in Praya and Dipliyes). The cormidia, which are separated by long 

 free internodes, are monogastric, each provided with a single siphon and a single cyston 

 only, besides numerous palpons. The rnedusiform structure of the gonophores is also 

 peculiar. These differences seem to be so important, that Dicymba might be separated 

 from the true Apolemidae as the representative type of a new family Dicymbidse. 



(ZOOL, CIIALL. EXP." 



1 T)icymhri = Double boat, nixvpfia. 

 -PART I.XXVTI. — 1888.) 



Ilhbli 27 



