OF THE WOODS HOLK KKWION. 



335 



Hydractinia polyclina Ag. Fig. 1 2. 

 ((Vint. Nat. Hist. r. s., iv, p: >7J 



Ti'iiiiliiuaiini'. Colony composed of thickly crowded persons arising from an incrusting plate beset 

 with jagged spines and overlaid with crenosarc. Hydranths slender, gradually increasing in size 

 from proximal to distal end, tentacles 

 numerous, filiform, arranged in sev- 

 eral closely approximated whorls, 

 which are so closely set as to appear as 

 one whorl at the base of the rather low 

 conical proboscis. Spiral zooids gen- 

 erally situated on the borders of the 

 colony and with a number of nenta- 

 tiM'yst batteries around the distal end. 



( !oii iixut/i i'. Gonophores borne 

 on sexual persons which are much 

 stouter and shorter than the hy- 

 dranths, and have numerous batteries 

 of nematocysts around the conical 

 proboscis, but no tentacles. No free 

 medusa'. 



f'lilnr. Hydranths white, tinged 

 with red. Gonophores, which give 

 the characteristic color to the colony, 

 bright red. c ^ 



Dintriliutiim. Found growing on ,,, //,,;.,.,//,,,,,,/ Ag '. A . Nutritive " person."' B. Repro- 



gaataropod shells inhabited by hermit rim-tire persons, c. Spinal zooids on fighting persons. 



crabs, on the bare rock, or on the piles 



of wharves. The writer has found them among the colonies of Tiiliulru-tacroctaon the V. S. Fish Com- 

 mission wharf at Woods Hole. 



I have carefully compared this species with //. rcliiiidla from England, and found that the two 

 are quite distinct as claimed by Agassiz. Aside from the characters as given by him I find that the 

 European form has very much larger hydranths than the American, and much less numerous tentacles. 



PODOCORYNIDJE (modified). 



Trophusome '. Hydranths with a single whorl of filiform tentacles around the base of a conical 

 proboscis. Hydrorhiza a reticulate network of stolons invested with perisarc and usually l>eset with 

 jagged spines. 



floiiotome. Gonophores growing in a circlet around the basal part of the hydranth body, and 

 producing fixed sporosacs or free medusa? with 4 radiating canals and 4 or 8 marginal tentacles with 

 eye-spots at their bases. 



STYLACTIS. 



Ti-ophosome. Hydranths sessile, without evident perisarc, slender, growing from a hydrorhiza 

 composed of a network of anastomosing tubes which are not covered with naked ccenosarc, and which 

 usually bear chitinous spines. 



fJoniisiitiie. Sporosacs borne on the hydranth body just below the tentacles, and producing 

 medusa: with 8 rudimentary 'tentacles and no mouth. 



Styiactis hooperi Srgrrlbw. Figs. 13 and 86. 

 (American Naturalist, xxxm, No. 394.) 



Tropltosome. Hydranths exceedingly slender and attaining a height when alive of alxitit three- 

 fourths inch. Tentacles in a single whorl, very variable in number, the average, according to Sigerfoos, 

 being 18 to 25. Hydrortma covered with a felting of diatoms, etc., but with no covering of naked 

 ccenosarc. 



