266 HYDROID^. Part IV. 



SECTION IV. 



TUBULARIA COUTHOUYI AG. 



Proles hydroidea. Adult. — We have always found this species in the same local- 

 ities, and under the same conditions, as Parypha crocea and Thamnocnidia spectabilis, 

 and never in pure sea-water, so essential to its very closely related European con- 

 gener, the Tubularia indivisa. It is usually found in clusters of not more than 

 four or five, and occasionally eight or ten, individuals, springing from a few closely 

 tangled, knotty, root-like tubes. Each stem (PI. XXIV. Fig. 1, a h c d) bears a 

 single head, and runs uj) from three to six inches, having, in the average, a diam- 

 eter of one twelfth of an inch, but tapering a little toward the base, where it is 

 connected with the diminutive, tangled, stolonic tubules. The whole stem, from 

 the base of the head to the lower extremity, is covered by a horny sheath, 

 which is more or less ringed, or jointed, sometimes very regularly, at intervals of 

 an eighth of an inch, or constricted once or twice, and then again smooth 

 throughout. 



The head resembles very closely that of Parypha crocea, described page 249, 

 except that the tentacles of the proboscis (PI. XXIV. Fig. 1, d j'j), amounting to 

 fifty, are disposed in three or four indistinctly defined series {Fig. 4, t f f f). 

 In each series they are successively shorter than the next inner, or higher ones, 

 and the outermost [f) are mere papillte. The head is much larger than that of 

 Paryjjha crocea or Thamnocnidia spectabilis, and so are also the stem and the 

 medusoids (b) ; in fact, Tubularia Couthouyi has an average of double the diameter 

 of these species, and its tentacles, when fully expanded, form a coronet measuring 

 an inch and a half across. 



The medusoids are jiresent, and full of completely developed young, from March 

 to December. It is not probable, however, that the, same head bears full-grown 

 medusoids all this time ; on the contrary, at one and the same date, some of the 

 largest hydroids bear only a few young buds, and others are crowded to the utmost 

 with highly-developed medusoids casting their young. The branches which bear 

 the medusoids are disposed in longitudinal rows, with three or four in each, so 

 that, transversely, they form three or four circles around the base of the proboscis. 

 The sexes are separate, on different stocks, and may be readily distinguished Avith 

 the naked eye by the shape of the medusoids, the males being elongate oval, or 

 pyrifonn {Figs. 2 and 3, b, and 5, d). and the females, globular or broadly oval 

 {Figs. 1, b, and 1», I*', d). 



