5° 



HYDROIDA 



Dicoryne conferta (Alder) as to confusion, and the two species have probably more than once been mis- 

 taken for one another. Both the species have styloid gonophores; but in Hcterocordyle they are ses- 

 sile, while in Dicoryne, when ripening, they assume cilia all over, develop two tentacles, and break 

 away. This is, unquestionably, a phenomenon of mere biological adaptation and cannot be recognized 

 as sufficient for distinction of genera as long as it is not accompanied by a thorough change of the 

 organization of the sterile parts of the colony. It is evident that Dicoryne and Hcterocordyle must be 

 drawn together into one genus, and moreover that this genus must be united with Bougainvillia. 



. boom. 



Text-fig. O. The habitat of Bougainvillia conferta in the Northern Atlantic. 

 (In the hatched regions the litterature denotes the occurence of the species without strict localities). 



Bougainvillia conferta (Alder). 

 1856 Eudcndrhon conjertum, Alder, A Notice of Some New Genera and Species of British Hydroid 



Zoophytes, p. 354, pi. 12, fig. 5-8. 



The colonies attain a height of up to 15 mm., and exhibit a rigid appearance. They have a 

 distinct main stem with short side-branches. The perisarc is vigorously developed and dark brown- 

 coloured. The small fusiform polyp attains a length of about 0.5 mm.; it wears about 16 tentacles in 

 a single whorl below the oral conically pointed portion. 



The gonophores are styloid and break away. When ripening, they assume a peculiar oviform 

 shape, develop two filiform tentacles, and put on a complete suit of cilia all over. The gonophores 

 are seated, gathered in a belt, somewhat below the apex of blastostyles, which arise from the hydro- 

 caulus or, in smaller numbers, from the hydrorhiza. The blastostyles show no indication of tentacles. 



