HYDROIDA 



23 



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

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



Material : 



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



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

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

 5 nnn. long, and 8 blastostyles a little branched, about i mm. long. A closer inquiry of the gonophores 

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

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

 doii prolifcr 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 Stemundsson as springing 

 from the tentacle bulb, are all gems of medusae; none of them can be made out as "initiura 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 gonophore. Therefore, we have to conciu' in the opinion of Hart- 

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

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

 takel in der Entwickelung stark voraneilt und schon fertig sein kann, weim der dazu geliorige Me- 

 dusenkorper nocli nicht deutlich in die Erscheinnng getreten ist". 



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

 odon) Chris finac Hartlanb (= Tubularia prolifcr 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, ^^- -^^'i ^^&- 3)- ^^"^ ^^ '^"^^ 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 Sa;mundsson is said to have 24 — 30. It is a matter of regret that 

 we onl\- 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 

 Tiibulariidac 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 pulchcr, it is in the first place owing to the express declaration of Bonne vie (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 ver\- little distinctive on material preserved.' 



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

 (1842), Corync frilillaria, and nuich 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 mav be that it really is a Corync; some features are even suggestive of Corync Lo- 

 vcni M. Sars; but the onh- thing the drawing shows us with full certainty, is that the l)olyp is no 



' The original spccinicii of Bonne vies Tubularia prolifer was wanting in the nuiseuin of the Kristiania university. 



C 



