50 



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 Heterocordyle 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 l)e 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 IJicoryi/f and Hclcrocordylc must be 

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



. boom. 



...1000 m. 



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

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



Bougainvillia conferta (Alder). 

 1856 Eudcndrium coii/rr/im/^ Alder, A Notice of Some New Genera and Sj^ecies of British Hxxlroid 



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



The colonies attain a heiglit of up to 15 mm., and e.xhilut a rigid appearance. They have a 

 distinct main stem with short side-brauclies. The perisarc is vigorousl)' 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 l)elow the oral conically pointed portion. 



The gonophores are styloid and lireak 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 liydrorhiza. The blastostyles show no indication of tentacles. 



