HYDROIDA 23 



large tentacle; there are four radial canals. The bell exhibits five exumbrellary stinging cell stripes. 

 The gonophores are developed on eight blastostyles faintly branched, a little more than 1 mm. long". 



Material : 



Iceland, Reykjavik. Near the shore (1 specimen). 



The specimen in hand is one of the original specimens investigated by Ssemundsson (1899). 

 It is an individual with hydrocanlus 30 mm. high. The polyp is fitted out with 25 proximal tentacles, 

 5 mm. long, and S blastostyles a little branched, about 1 mm. long. A closer inquiry of the gonophores 

 gives a picture somewhat different from that drawn from the explanation of Saemundsson. In the 

 first place the umbrella of the medusa is not quite symmetrical, but somewhat oblique, as in Hyboco- 

 don prolifer L. Agassiz. At first only one tentacle, not two, is developed on the large tentacle bulb 

 (Tab. II, fig. 16); the "corpora acuminata et duo ovata", mentioned by Ssemu ndsson as springing 

 from the tentacle bulb, are all gems of medusae; none of them can be made out as "initium tentacu- 

 lorum novorum" belonging to the original medusa. Wherever at the first glance two tentacles seem 

 to occur on the bulb, a closer research will show that one of them in fact belongs to the bud of a 

 new medusa on the bulb of the gouophore. Therefore, we have to concur in the opinion of Hart- 

 laub (1907) and subscribe to his explanation of the apparent occurrence of two tentacles with Hybo- 

 codon prolifer as satisfactory for the species in hand, that "bei der Knospung von Hybocodon der Ten- 

 takel in der Entwickelung stark voraneilt und schon fertig seiu kann, wenn der dazu gehorige Me- 

 dusenkorper uoch nicht deutlich in die Erscheiuuug getreten ist". 



The conditions of gonophores described show a much nearer relationship to Tubularia [Hybo- 

 codon) Christ inac Hartlaub (= Tubularia prolifer Bonne vie 1899). Hartlaub's drawing of Hybo- 

 codon Christinac (1907, fig. 98) is, according to the statements cited, easily reconcilable to the figure a 

 little more skeletonlike given by Ssemundsson (1899, ta b- *V, fig. 3). Nor is the difference between 

 the polyps very great; Bonne vie (1899) states for her specimen 14 proximal tentacles, about 10 mm. 

 long, while the species stated by Ssemundsson is said to have 24 — 30. It is a matter of regret that 

 we only know the length of the proximal tentacles of the specimen in hand. But on account of the 

 great contractility of the tentacles, no particular systematical importance can be attached to their 

 length, and as far as the difference of numbers of the proximal tentacles is concerned, we see in other 

 Tubulariidae within easy reach such a variety that the difference quoted by itself cannot justify any se- 

 paration of species. When Tubularia Christinac is nevertheless maintained as a separate species beside 

 Tubularia pu/cher, it is in the first place owing to the express declaration of Bonnevie (1899) that 

 her specimen has no collar under the hydranth ; such a collar is, on the other hand, strongly developed 

 in Tubularia pulchcr, though at the first glance it may seem very little distinctive on material preserved. 1 



Hartlaub (1907) holds that the medusa is identical with the medusa drawn by Steenstrup 

 (1842), Corync fritii/ar/a, and much is speaking in favour of the correctness of this supposition. On the 

 other hand, the polyp described by Steenstrup, in the same place and by the same name, cannot 

 be identified. It may be that it really is a Corync; some features are even suggestive of Corync Lo- 

 veni M. Sars; but the only thing the drawing shows us with full certainty, is that the polyp is no 



1 The original specimen of Bonnevies Tubularia prolifer was wanting in the museum of the Kristiania university. 



