[163] THE HYDROIDS l8l 



SYSTEMATIC DISCUSSION. 



The writer deems it unnecessary to attempt a complete syn- 

 onymy of the well known European species contained in the 

 Harriman collection and considers it sufficient to give,_/r5/, and 

 in all cases, the original reference to the species ; second, all 

 obtainable references to the occurrence of the species on the 

 Pacific Coast of America, and, third, a reference to verify the 

 * General Distribution ' as given in the table just discussed. In 

 this latter case only one reference will be given to verify the 

 occurrence of a given species in each of the regions included 

 in the right hand portion of the table. 



As to the classification employed in this report, it seems best, 

 on the whole, to pursue a conservative course, following pretty 

 closely the lines laid down by the able British naturalists, 

 Hincks and Allman. While it is true that the classification is 

 in an unsatisfactory state, the writer does not feel that a thor- 

 ough revision of the entire group of Hydroida should be at- 

 tempted here, and frankly confesses his conviction that recent 

 attempts in that direction have not been successful, though each 

 contains valuable suggestions. Levinsen, for example, has 

 made a notable contribution to our knowledge of the Campanu- 

 linidas in his able and careful exposition of the differences in 

 the opercula of various species, but his genera founded solely on 

 these structures appear to be artificial, as usually happens when 

 a single character is made the basis of classification. 1 In his 

 terse characterization of the genera of Sertularidse this author 

 has been most fortunate, as well as in his masterly clearing up 

 of the mystery concerning the gonosome of Lafoea. 



Schneider, 2 also, has attempted to rearrange the Hydroida on 

 a logical basis. Instead of multiplying groups, as has been the 

 tendency of late, he has, in my opinion, gone far to the other 

 extreme, uniting families that almost any other student acquainted 

 with the group would regard as surely distinct. It seems un- 

 likely that he will be followed in uniting such groups as the 

 Tubularidse and Pennaridse in a single family, although one 



1 Meduser, Ctenopherer og Hjdroider fra Gronlands Vestkyst, Copenhagen, 

 1893. 



2 H ydropolypen von Rovigno, nebst iibersicht iiber das system der hydro- 

 polypen in allgemeinen. Zool. Jahrb., Syst. Abth., Vol. x, 1897. 



