IV. HYBOCODON PROLIFER 



TWENTY FIGURES (THREE PLATES) 



STRUCTURE AND HABITS 



Hybocodon is one of the Tubularian hydroids with the gen- 

 eral structural characteristics of that group, but has especial 

 interest in the fact that the medusae which are produced give 

 rise to other medusae by budding. Thus, not only the polyp 

 produces buds asexually but the medusae do the same thing. 

 The hydroid is recorded as having been found but rarely on 

 our Atlantic coast, but it must be fairly abundant in places 

 about Cape Cod and elsewhere since the medusae are sometimes 

 very abundant. Agassiz ('62) found it in very quiet and pro- 

 tected waters about Nahant and believed its normal habitat 

 was in deep water in places protected from waves and strong 

 currents. Such a habitat would explain why the hydroid is 

 rarely captured, for such a position would render it difficult to 

 obtain by dredging. 



The hydroid (fig. 36) is a solitary form, or at most a colony 

 consists of a few unbranched stems connected by branching 

 stolons. The hydranth at the end of the stem is rather large, 

 has a single row of basal tentacles and a double row about the 

 mouth. Figure 36 is drawn from a preserved specimen and is 

 satisfactory in showing the general form; a better representation 

 is the figure of Agassiz ('62, vol. 4, Plate 25) which is drawn from 

 life. The medusae arise by budding from the sides of the 

 hydranth between the basal and apical series of tentacles, and 

 are produced in large numbers from a single polyp. The medusae 

 have four radial canals with swollen bulbs at their bases, but 

 only a single tentacle which extends from one of the bulbs. 

 The bulb at the end of this tentacle is very much enlarged, and 

 this, with the single tentacle extending from it, gives the medusa 

 a very unsymmetrical form. Figures 37 and 38 are drawings 



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