186 BULLETIN OF THE 



however, it would be unsafe to insist on the identity of these with the 

 European species. 



Among the Sertularina;, nineteen species belong to the Sertularidae 

 and twenty-eight to the Plumularidae. Of the nineteen species of 

 Sertularidae -ixteen have not yet been met with beyond the area inves- 

 tigated by the Explorers, while three are undistinguishable from the 

 following European species: Sertularella Gayii and its variety, rohusla ; 

 Sertularella polyzonias ; and Sertularella tricuspidata. 



The collection is especially rich in the Plumularida?, no less than 

 twenty-eight out of the seventy-three species of which the collection is 

 composed belonging to this beautiful family. Two of these would seem 

 to be common to both sides of the Atlantic ; for though it is true that no 

 gonosome is present in either of them, their trophosomes are undistin- 

 guishable from those of the Antennularia ramosa and Plumvlaria catk- 

 arina of the European shores. 



Among the Gymnoblastea contained in the collections, the gonosome 

 is present in a large proportion of species. So also a large proportion 

 of the Plumularida: are provided with their gonosomes and present some 

 interesting and beautiful modifications of this part of the hydroid colony. 

 It is remarkable, however, that the gonosome is absent in almost every 

 instance from the other Calyptoblastie forms. Among the fifteen species 

 of Campanularinae the gonosome occurs in only one ; while among the 

 nineteen species of Sertularidae it is present in only two, unless a remark- 

 able structure, which will be described in the detailed report, is rightly 

 referable to this part of the colony, and then a third species must be 

 included among those Sertularidas in which the gonosome is preserved. 



The two species of Sertularidae in which the gonosome is undoubt- 

 edly present are common to both sides of the Atlantic, while not oidy 

 those, but the single example of the Campanularime, in which it also 

 occurs, are from some of the deepest dredgings made. 



January, 1873, 



