278 SYNCORYNE MIRABILIS. 



*^* 4. Syncoryne MiEABiLis, Agassiz. 



CoRYNE MIRABILIS, — Ayussiz, Contr. Nat. Hist. U.S., vol. iv, p. 185, pis. xsvii — xx. 

 Clark, Mind in Nature, p. 77, figs. 40 — -12. 



TROPHOSOME. — Hydkocattlus consisting of branching stems, wliicb, without 

 any distinctly differentiated iiyduohuiza, adhere to some fixed object for a greater or 

 less extent of their length, and then become free, forming irregularly ramified tufts, 

 which usually attain a height of about half an inch ; peeisauc smooth. Hydhanths 

 with about sixteen tentacles. 



GONOSOME. — Medusa borne on the body of the hydranth, either from among 

 the tentacles or from a point just behind the most posterior ones. They are of two 

 forms, free and fixed; the free gonophores (produced in the earlier months of the year) 

 have a wide umbrella, with well-developed marginal tentacles, set with irregular 

 clusters of thread-cells, and provided with an ocellus in the basal bulb ; manubrium of 

 moderate size. The fixed gonophores (produced at a later period) have a deep thimble- 

 shaped umbrella, imperfectly developed marginal tentacles without ocelli at the base, 

 and a very large manubrium, which, Avith the generative elements developed in its 

 walls, nearly fills the cavity of the umbrella, and even projects beyond it. 



Development of Gonosome. — January to May. 



Habitat. — Attached to rocks, sea-weeds, and floating timlier iu the sea and in the brackish 

 water of the estuaries of rivers. 



Localili/. — Atlantic shores of North America, Agassiz and Ckrk. 



I have compiled the above diagnosis from characters selected from tlie elaborate description 

 of the species by Agassiz, whom, along with Professor Clark, I have followed in referring the two 

 forms of gonophores described iu the diagnosis to one and the same species. I cannot, however, 

 but think that for so remarkable a fact, unsupported, as it is, by the analogy of other hydroids, 

 stronger evidence is needed than any that has been adduced by the American zoologists. Until 

 specimens shall be found in which the two kinds of gonophores exist simultaneously, or until 

 these can be shown to be consecutively de\'eloped from one and the same colony confined in our 

 aquaria, or otherwise subjected to continuous observation, we can scarcely accept the specific 

 identity of the two forms as proved.^ 



' Mr. Ilincks, liowever ('Brit. Hydr. Zoopli.,' p. 54), not only adopts the views of Agassiz and 

 Clark upon tliis point, but refers the Sijncorijne mirahilis, A gas., to the Sijncorync gravatu, "Wright, 

 regardins; the latter as the arrested condition of the former. 



