in UKTIN <>K Till-: LfNITKl) STATUS FISH rn.\l.\l issiu.N. 



or less extensively on hydroids. Dr. Kdwin Linton has several times called my 

 attention to the fact that he often finds hydroids in the stomachs of fishes while 

 examining them for parasites. 1 am inclined to think, however, that hydroids do 

 not constitute a very important item in the dietary of our food-fishes, and am rather 

 of the opinion that the economic importance of hydroids lies in the fact that the 

 presence of these forms in quantities in a given region is of value as an indication of 

 abundance of food for fishes in the shape of small crustaceans. It is known that 

 many kinds of hydroids live very largely on minute crustac-ea, and it follows that 

 Where the hydroids thrive the fishes will also lindan abundant food supply, especially 

 in the earlier stages of their development. 



The author -is indebted to many naturalists for material that he failed to securo 

 himself, and has endeavored to briefly acknowledge these fcivors in their proper- 

 connection in the body of the text. 



STATK I'MVE'UMTV OF IOWA, Ani/uxl 10, 1900. 



Kill In /III' J'ililli/ii-x nf Ill/ilroiiln fiill'iul in Hi," U'lHiilx Hull' fi'i/ifin. 



A. Hydranths anil >:' mophores not provided with special chitinons receptacles. 



a. Hydra n ills with MM I tern I lilil'cirni tentacles CI.AVID.K. 



<('. Hyilruuttis with u single whorl of li!il'(ini] lenlaclcs. or two or more closely approximated whorls. 



around base of proboscis, which lni.i, r l]l easily he mistaken for a single wliorl. 

 b. Proboscis conical. 



o. Colony regularly branched BotjGAisviu.iDvE. 



<'. Colony not branched. 



tl. Hydrorhi/a- composed of incni.stintt, aillierenl tubules overlaid with a Him of I'lenosarc. 



HYDRACTIXIDJ:. 



'/'. Hydrorhizie not mutually adherent and not overlaid with n layer of co-nosarc PODOCORYNI&4E. 



//. I'roltoseis trumpet-shaped or hemis|iherical. the distal portion beinif the bell of tile trumpet or 



e<in:itor of I lie hemisphere EUDENDKID.S. 



'.i". Hydranlhs w'ith more than <-:ie w liorl of liliform tentacles. 

 //. A dislinet tube of horny perisan' around the stem. 



<. Distal tentacles in two distinct whorls TITBULARID.*:. 



f. Distal tentacles not in two .list inn horls HYBOCON1DJ!. 



/i'. No distinct j.erisarcal tube: stem conspicuously cunaliculated: probosiMs large COEYMORPHID*. 



'". Hydrant hs with e.ipitale tentacles only SYNCORYNID*. 



a"". Ilydranths with a basal row of filiform tentacles, and with capitate tentacles on the proboscis PENNARID*:. 



A'. It'ydranths and iionophores provided \\ itli special ehitinous reeejitacles. (Hydrotheca- and ^onangia.) 

 o. Hydrotheca- \\ith distinct pedicel, anil with a septum partly dividinn the hydrothecal cavity from 



the cavity of the pedicel CAMPANULARID*. 



a'. Hydrothec;e with an opercnlnm compoKed of con verging seKinents CAMPANULINID^:. 



a". Hydrotliee:e deep, witli pedicels: or ses/ile, and without the septum LAFOSID^:. 



ii'"'. llydrotheea- reduced to saucer-shaped hydrophoivs ornamented with a necklace of bright dots, 



and much too shallow to accommodate the hydranths HAI.ECII>.E. 



<"''. llydrotheea- sessile, mid adnate by their sides to the branches on which they are placed. 



l>. llydrotheea- arranged OTI lj->th sides o! the branches SERTULARID^. 



' I,'. Hydrothcea- arranged on KM side only of the branches PUIMULAR1M5. 



CLAVIDAE. 



Trophosome. Ilydroraulus lininrhi'il, simple, or not evident. Hydranths with elongated terete 

 bodies, upon which the smooth filiform tentacles ;uv sriitu-ivd, or arranj;ed in an ill-<lefined spiral. 



<inii,ixiin\ Gonophores growing from the hydrorhiza, hnuiclu's, or body of the hydranths, am^ 



not pniihicin;' OIT mcihisiii 1 . 



Ki'if tn t/i'ni'i'ii f f ' '/tii'!'/:r I'nnilff ill Woodt lft>l< I'l'tjuni. 



rolony un branched. ll\ - di'anth si ems not inclosed in perisare:il tubes Clara. 



Colon > profusely Immcli-.l fimvlytophnrn. 



