144 



HYDROIDA II 



The gonothecae are set on the upper side of the branches. They are pear-shaped, with rudi- 

 mentary neck and broad aperture. 



Material : 



"Ingolf" St. 31 66°35' N., 55°54' W., depth 88 fathoms 1,6" 

 - - 34 65°i7' N., 54=17' W., - 55 - - 



Greenland: Davis Strait, — 100 — (without further details) [type specimen]. 



Iceland: Skagi, — 20 — [labelled Thiijaria lonchitis\ 



Dyrafjord, — 15 — 



In all probability, this species also will prove to have a pinnate development stage, like the 

 other, spiral Tlinjaria species. In the arrangement of the hydrothecae, Thujaria alternitJieca forms a 

 parallel to Abich'tiaria [7) //tsra (Johnston), and it is interesting here to note how the hydrothecae, 

 owing to their extremely close accumulation, thrust their opening part to one side or the other from 

 the base of the next following. An investigation of the tip of the branch shows that this is a secon- 

 dary phenomenon. The liydrothecse are to begin with symmetrically situate, with their s\nimetrical 

 plane parallel to the branch axis; only on the formation of a new distal hydrotheca is the aperture 

 of the one behind it thrust out to the side. We have here, then, a typical instance of convergenc\-, 

 as towards Ad7etinaria{7)/usca, which cannot be taken as evidence of closer relationship, and thus does 

 not afford any justification for uniting the two species mentioned, and other multiserial forms in a 

 special genus Sclaginopsis\ any such would also have to include species with and those without blind 

 sack, which can hardly be considered permissible. 



600 m, looa m. 



I'ig. lAXVIII. Find.s of T/niJ.nia alternithcca. 



