THE PLUMULAKID.E. 47 



and the retention of what might be called protozoan characters on the part of the individual cells. 

 This being true, it is certainly possible, indeed not exceedingly improbable, that in some instances 

 the protozoan method of reproduction should still be potentially retained and brought into activity 

 under certain combinations of circumstances which would render it of marked benefit to the colony. 



SYSTEMATIC 1 'DISOUSSIOK 



Family PLUMULARID.E Louis Agassiz. 1 



Troplwsome. The hydranth with a conical proboscis and a single verticil of filiform ten- 

 tacles. Hydrothecu', found on one side only of their supporting ranmli (hydrocladia), and 

 always more or less adnate to the latter. Nematophores always present, three being usually 

 associated with each hydrotheca and others variously situated on the hydrocaulus. 



Gonosome. Gonophores always inclosed in gouangia, which may be either unprotected, pro- 

 tected by special nematophorous branchlets, or inclosed in corbulse which are highly modified 

 hydrocladia. Free medusa- are never formed, the ova developing into ciliated planula- within 

 the gonangia. Colonies almost always unisexual. 



Previous to the great work of the elder Agassiz, three genera Plumularia, Antennularia, 

 and Agla-oplit-niit all of the plumularians then known, were included with other cnlypteroblastic 

 forms in the family Sertulariada-. McCrady, in his "Gymnophthalmata of Charleston Harbor," 

 1837, had already pointed out the desirability of separating these forms from the others, a 

 suggestion carried out finally by Louis Agassiz, in which he was followed by Hincks, Allnian, 

 and indeed practically all the more prominent writers up to the present time. Several British 

 writers, for example, Hiucks- and Bale n , have written the word "Plumulariida 1 ," but the original 

 spelling of Agassiz is here retained, in which the present writer agrees with Kirchenpauer 4 , 

 Altaian 5 , and von Lendenfeld." Allman 7 constituted a "legion" I'lumulariiia', in which arrange- 

 ment he is followed by Marktauner-Turneretscher." This legion is coextensive with the 

 previously named family IMuuiularidic. 



The present writer is inclined to adhere, so far as possible, to the zoological arrangement 

 most affected by his countrymen, in which the groups are arranged in classes, orders, families, 

 genera, and species; and to avoid other terms as well as the use of subfamilies, subgeuera, 

 and subspecies, which often tends to confuse the student rather than to render him any real 

 service. 



The Pla.mularid.8e constitute a perfectly well defined group of the Calypteroblastea, related 

 on the one hand to the Sertularida', and on the other to the Hydroceratinida-, a family recently 

 instituted by Prof. W. Baldwin Spencer to accommodate a remarkable Australian hydroid, 

 C1<ithro:<>(i>i icilsoni, which, although widely different from the Pluinularidu 1 in many respects, 

 resembles it in having what seem to be true nematophores containing true sarcostyles. The 

 relationship is still more close to the family Zygophylacidse instituted by Mr. John J. (^uelch 11 

 to accommodate a new form found on the Atl mtic cable off' the Cape Verde Islands, charac- 

 terized by a trophosome greatly resembling Altaian's family Perisiphonidae, and having a pair 

 of structures which are apparently nematophores at the base of each hydrotheca." 1 



It is probable that over one-fourth of all the hydroids of the world belong to this group, and 

 quite possible that the proportion may reach a third. Deep-sea investigations tend to raise the 

 proportion of Plnmularida-. In the Clialleiif/cr collection about 2S per cent of all the hydroids be- 

 long in this group. Taking the two regions in which the hydroid fauna has been most thoroughly 



1 Contributions to the Natural History of the United States, IV, p. 358. 

 -British Hydroitl Zoophytes, p. i'7!i. 



3 Australian Hydroid Zoophytes, p. 120. 



4 Ueber die Hydroidenfamilie Plumularidir (title). 



5 Memoirs of the Museum of Comparative /oology, V, >.'<>. '2, p. 29. 

 "The Australian Hydromedusa-, Pt. 4, p. 472. 



7 Chiilteni/rr Report, Hydroida, Pt. 2, p. lii. 



"Die Hydroiden des k. k. naturhistorischer Hofnmseiims, p. 249. 

 'Annals and Magazine of Natural History, July, 1885, p. 4. 



10 1 have myself found structures greatly resembling iiematophores in auotln-r species of this family, Lafoi : a 

 conrallaria Allman. 



