[i67] 



THE HYDROIDS 



a conical, or rather conoid, proboscis and about sixteen tentacles all of 

 which appear to be held more or less erect. 



Gonosome. — Gonophores borne either on the stem or hydrorhiza, 

 more frequently the latter, oval in shape, borne on pedicels enveloped 

 in a chitinous perisarc which ends in a slightly expanded collar a little 

 below the gonophore. The specimens collected were female and the 

 gonophores were packed with apparently mature ova. 



Color. — The label accompanying the specimens bore the following 

 statement: "Bright orange throughout, heads, stems and all." 



Distribution. — ^Yakutat and Sitka, Alaska. Collected by the Har- 

 riman Expedition in considerable quantities. 



This species can be sharply distinguished from its British relative 

 by the very distinct and beautiful annulation which covers the entire 

 stem and branches. It is much less extensively branched than the British 

 species, and the gonophores are more generally borne on the roots. 



The structure that I have designated above as a ' pseudo-hydrotheca ' 

 is of considerable morphological interest, for it may throw light on the 

 origin of the hydrotheca. The extension of the chitinous perisarc of 

 the stem over the body of the hydranth appears to be attached to the 

 latter. A true hydrotheca would be formed if the perisarc around the 

 hydranth body should become thicker and detached. 



Family EUDENDRIDy^. 



Tropkosome. — Colony branching. Hydranths with a single whorl 

 of filiform tentacles and a trumpet-shaped or hemispherical proboscis 

 which is expanded distally and contracted proximally, thus being 

 sharply distinguished from the hydranth body. 



Gonosome. — Reproductive elements developed in fixed sporosacs at- 

 tached to a usually more or less degenerated hydranth body below the 

 tentacles. 



This family contains but one genus, Eudendrium., which needs no 

 further definition. 



EUDENDRIUM VAGINATUM Allman. 



(Plate *¥, figs. 3-6.) 



Eudendrium vaginatum Allman, Annals and Mag. Nat. Hist., Third Se- 

 ries, Vol. XI, p. 10, Jan., 1863. 



As the gonosome of this species has not heretofore been described, 

 the following is inserted here : 



Gonosome. — Gonophores (female) in dense clusters around the 

 bodies of hydranths that are usually devoid of tentacles. Each go no- 



