52 



HYDROIDA 



calls our attention to the interesting fact that the polyps are basally attached to the pseudohydrotheca 

 by a whorl of small chitinous bodies similar to that met with in Halcciidae, Plumulariidae, Lafoeidae, 

 and Campanulariidae ; they actually attach the supporting lamella to the polyp case. Systematically, 

 however, hardly any particular importance can be attached to this character. The chitinous bodies 

 occur on the passage from the pseudohydrotheca to the hard periderm of the stem. Also the periderm 

 of the stem has, in most species of Perigonimus a jellied cover, to which a lot of foreign bodies fasten 

 themselves so as to give the colony a foul appearance. 



The stinging cells in the tentacles of the Perigonimus-STpecies show attempts at an arrange- 

 ment by belts. But it is not here so pronounced as in the Eudendriidae and the thecaphore hydroids. 

 This criterion, together with the pseudohydrotheca, suggests that Perigonimus must be more nearly 

 related to the thecaphore hydroids than most other athecate hydroids. 



Perigonimus repens (Wright) Allman. 



1857 Eudendrium repens, Wright, Observations on British Zoophytes, p. 84, pi. 82, fig. 8—9. 

 1864 Perigonimus , Allman, On the Construction and Limitation of Genera among the Hy- 



droida, p. 365. 

 nee 191 1 — , Broch, Fauna droebachiensis, p. 14. 



From the reptant stolons proceed thin polyp stems, up to 5 mm. long, more rarely dichotomi- 

 cally divided so as to bear two polyps. The polyps are about 0.5 mm. long, broadly fusiform, with 

 4 — 12 tentacles placed in a whorl, and surrounded below the tentacles by a thin jellied pseudohydro- 

 theca, which is sometimes hardly observable. The polyp stems are wholly without rings, and all but 

 without wrinkles, and provided with a dark-coloured, but thin perisarc, which, on account of bottom 

 particles appendant, convey the impression of being granulous. 



The gonophores are developed into free medusae; when breaking away, they have two ten- 

 tacles and a well-developed, solid umbrella. The gonophores are borne individually on stems 0.2 — 0.3 

 mm. long, proceeding from the hydranth stems; on one hydranth stem is generally developed one 

 gonophore at a time, sometimes a couple of gonophores simultaneously. 



Material : 



The Faroe Islands, Sorvaag. Depth 14— i6 r / 2 fath. (on Nucula nucleus). 



Certainly it is not this species that is delineated and described by the name of Perigonimus 

 repens in Fauna Droebachiensis (Broch 1911). A comparison with the excellent drawings of the 

 species with Jaderholm (1909, Taf. I, Fig. 15 — 16), at once shows us the difference. The species 

 described and delineated from the Kristianiafjord has a stiff and robust structure; its perisarc is solid 

 and the colonies are open rhizocaulome formations; most probably the specimens in question should 

 have been referred to Perigonimus muscoides M. Sars. Perigonimus repens, on the other hand, has 

 thin closely set, irregularly curved polyp stems. Besides, the colonies from the Kristianiafjord bear on 

 the hydranth stems numerous gonophores without stalks, while the few gonophores of Perigonimus 

 repens are borne on distinct small stalks covered with perisarc. 



