326 



HYDROIDiE. 



Part IV. 



SECTION VIII. 



DYNAMENA PUMILA LAMX. 



All the Hydroids of our coast, described in the preceding pages, exhibit such 

 distinct specific differences fi'om their European representatives, that they may 

 readily be distinguished. Not so with our most common Dynamena. After 

 repeated comparisons Avith di'ied specimens from the shores of Europe, I could find 

 no difference. Not satisfied, however, with this evidence, I requested my friend, 

 Captain James Anderson, to bring me living specimens of the European Dynamena 

 pumila, which he obtained through the kindness of Mr. Thomas Moore of Liverpool, 

 and brought safely to Cambridge, where I compared them anew with specimens 

 from the Bay of Boston. The result of this renewed comparison was, however, 

 the same. I can perceive no constant difference between them. 



Proles Hi/droidea. Adult} — There is no Hydroid on the coast of New England so 

 common as this; from high to low-water line, wherever the common olive Fucoids 

 grow, Dynamena pumila flourishes in the greatest profusion upon them, and among 

 them upon the rocks. From September to April, through the cold months, the 

 hydrte alone are to be found (PI. XXXII. Fig. 1), but from May to July, the 

 reproductive and sterile forms are alike abundant. When attached to the flat 

 fronds of searweeds, the horizontal creeping stolon {Fig. 1) is quite conspicuous, 



' References to Dtnamena Lamx. 

 Dynamena Lamx., Bullet. Soc. Phil., Paris, 1812. 

 " Histoire des Polypiers Corall. Flex., 



1816, p. 11. 

 Expos. Methodique, 1821, p. 11. 

 " Fleming, British Animals, 1828, p. 543. 



" Blainville, Diet. Sc. Nat., 1830, LX. 



p. 448. 

 « Blainville, Manuel d'Actinol., 1834r- 



1836, p. 484. 

 Sporadopyxis, Ehr., Corallenthiere, Verh. Acad. Wiss. 



Berlin, 1834, p. 74. 

 Sertularia, Linn., Fauna Greenland., 1761, p. 540. 

 " " Syst. Nat., 1767, p. 1306. 



" Pallas, Elenchus Zooph., 1766, p. 106. 



" Solander and Ellis, Zooph., 1786, p. 32. 



Sertularia, Gmelin, Linn. Syst. Nat., 1788, 13th ed., 



3844. 

 " Turton, British Fauna, 1807, p. 212. 



" Oken, Lehrbuch, 1815, p. 92. 



" Lamarck, Animaux sans Vert., 1816, 



p. 114. 

 " Bosc, Hist, des Vers., 1830, 2d ed., p. 94. 



« Lister, Phil. Trans. Roy. Soc, 1834, 



p. 371. 

 " Milne-Edwards, in Lamck. An. sans Vert., 



2d ed., 1836, p. 136. 

 " Johnston, Brit, Zoiiph., 1838, p. 121, and 



1847, 2d ed., p. 61. 

 " Alder, Catal. Zociph., Northumb. &c., 



1857, p. 24. 

 " Bars, Nyt Mag. Naturvid., 1856, p. 163. 



