REPORT ON THE SIPHONOPHOR^E. 91 



In the numerous voyages which I have made during the past twenty-five] years, in 

 order to complete my System der Medusen (compare the Preface to that Monograph), I 

 have found also many opportunities of examining a great number of Calyconectae belonging 

 to all the genera described in the following pages. The richest harvest was reaped during 

 my residence in the Canary Islands (December 1866 to February 1867), where I was 

 able to examine accurately a great number of new or imperfectly known Monophyidae, 

 Diphyidae, and Polyphyidae. I there traced the complete metagenesis of many typical 

 genera and the ontogenetic connection of monogastric and polygastric Calyconectae. 

 Supported by this rich personal experience, I have in the following pages attempted to 

 (rive a more correct definition of genera and a more natural arrangement than has hitherto 



o o o 



been possible. 



Nectophores. — The Calyconectae differ from all other Siphonophorae in the complete 

 absence of any pneumatophore, so that the nectophores are the only organs of locomotion. 

 The polygastric Calyconectae bear on the top of the long tubular stem either one or two 

 large nectophores (Monophyidae and Diphyidae), rarely a biserial nectosome, which is 

 composed of two opposite rows of nectophores, four to six or more (Desmophyidae and 

 Polyphyidae). The locomotion of the monogastric Calyconectae is effected usually by the 

 subumbrella of the gonophores (Eudoxidae) ; but in the Ersaeidae the first-formed 

 gonophore loses its sexual functions, and acts as a "special nectophore." 



The larva of the Calyconectae, which develops from the fertilised egg, and which we 

 call Calyconula (PI. XXVII. figs. 8-11), is a bilateral medusoid person, the manubrium 

 of which lies outside the campanulate umbrella, apparently protruded through a ventral 

 fissure of the latter. 1 The " primary nectophore " of this Calyconula often (perhaps 

 always) becomes detached, and replaced by a secondary nectophore, which is often 

 heteromorphous. 



The number, arrangement, and form of the nectophores in the different Calyconectae 

 are very variable, and serve mainly for the distinction of genera. Regarding the 

 general form of the nectophores, we may distinguish two different main groups, Sphaero- 

 nectariae and Cymbonectarias ; the umbrella of the former consists of a very soft jelly, 

 and is subspherical, mitriform or reniform, always devoid of distinct edges, with rounded 

 surface. The umbrella of the latter, on the contrary, has always a definite geometrical 

 form, and is polyhedral, either pyramidal or prismatic, with polygonal faces and sharp, 

 often denticulate, edges ; its jelly-substance is rather hard and firm, often cartilaginous. 



Nectosac and its Canals. — The original form of the muscular subumbrella in the 

 Calyconectae is hemispherical, but usually in correlation with the fundamental form of 

 the nectophores (primary as well as secondary umbrella) it is more or less bilateral, 

 and at the same time tuiadriradial ; the latter structure (inherited from the ancestral 

 Anthomedusas) is indicated by the constant four radial-canals of the subumbrella ; 



1 7, Taf. xvi. figs. 12-21 ; 85, Taf. vi., vii. ; 86, Taf. xvii. figs. 6, 7. 



