HYDROIDA 



47 



The reptant stolons are covered by a continuous chitinous coenosarc, whose surface is studded 

 with small prickles, among which occur larger chitinous spines about 1.5 mm. high, provided with lon- 

 gitudinal rows of more or less regular small teeth. The large spines now and then show a tendency 

 to divide at the apex. The polyps are up to 4 mm. long, whitish or faintly reddish, with 20—30 

 tentacles in a dense whorl below the oral portion. The tentacles form a belt which appears double 

 because of alternating displacement. Spiralzooids without tentacles occur along the margin of 

 the colony. 



The gonophores are cryptomedusoid, placed, to a number of 3 or 6, round reduced polyps with 

 rudimentary tentacles. 



Material : 



Greenland: Upernivik, depth 80 — 90 fathoms without particular data, from a cod's stomach. 

 Skagerrak: the channel near Vinga (Bohuslan), depth 50 fath. 



Hydractinia echinata in its large chitinous skeleton-spines (Tab. I Fig. 9 and 10) has a very 

 typical armour impeding a confusion with other northern species. It is an Atlantic-boreal species, 

 showing a great power of enduring both high and low temperatures. It occurs very frequently in 

 the North Sea, along the coasts of Great Britain and Ireland, goes to the south as far as into the 

 Mediterranean, and is also found on the east coast of North America. The species belongs to the 

 litoral region and almost always goes together with Eupagums Bernhardus, on whose house it settles. 

 When we consider the distribution of the species along both sides of the northern Atlantic, we must wonder 

 that it has not yet been observed at the Faroe Islands, and that only a single specimen has been met 



._ 1000 m. 



Text-fig. N. The occurrence of Hydractinia echinata in the Northern Atlantic. 

 (The hatched parties denote according to litterature a scattered allthough common occurence). 



