HYDROIDA II jc 



internodium, surrounded by a pair of supraealyeine sareotheea; on the distal part of the internodium 

 and an unpaired median proximally; between this and the base of the hydrotheea arises a sarcotheca- 

 bearing branch, which bends forward over the hydrotheea, and has on its convex (outer) side a row 

 of sarcothecse. The sarcotheca-bearing branch of the basal hydrotheea developes into a secondary 

 hvdrocladium of the same appearance as the primary, but somewhat finer. Also in the exterior 

 sarcothecal branches hydrothecse may be developed. The hydrothecse are fused throughout their 

 basal half with the branch; the distal portion forms an angle with the basal, and widens some- 

 what towards the aperture. The margin is furnished with 9 or : i teeth; a large median proximal 

 (abcladial), beside this as a rule a couple of smaller ones, then two well marked, and finally there are 

 distally (adcladially) a pair of large teeth of the same size as the proximal, and between them a couple 

 of quite small ones. 



The gonothecas are attached by a short, often almost rudimentary stalk to the stem; viewed 

 laterally, the gonotheca is asymmetrically egg-shaped or oval, with a distal lateral opening; seen from 

 the front, they are oval, distally often broadly rounded; the aperture is round. At times there may 

 be some approach to formation of ail "upper lip" above the mouth. 



Material: 



"Ingolf" St. 44 6i°42' N., 9°36' W., depth 545 fathoms 4,8° 

 - 98 6 5 ° 3 8' N, 26° 27 ' W, - 138 5,9' 



r- r^° 



The new colonies brought home by the "Ingolf" show that the Halicornaria pluma Broch 

 ( 1903 p. 8) described as distinct species is really only a somewhat older stage of Nematocarpus niniu- 

 liferus (Allman); we have now colonies showing the next stages through which they pass over to 

 the possession of secondarily branched hydrocladia (fig. XXXVII a). Here also the species retains its 

 peculiar nude posterior side, whereas the front appears even more furry than in young colonies. There 

 are certain signs which seem to indicate that a primary hydrocladium may bear several secondary 

 ones. Halicornaria pluma was established chiefly on the strength of the fact that the basal sarcotheca- 

 bearing branch of the hydrocladium has a hydrotheea, whereas the remaining sarcothecal branches 

 lack hydrothecse. The present colonies now show that this was merely the forerunner of the second- 

 ary hydrocladium, which gradually developes new hydrothecee with sarcotheca-bearing branches out- 

 side the first 1 . At the same time, however, we find a hydrotheea with its corresponding sarcothecal 

 branch developed at the second, often also at the third hydrotheea, and it is therefore highly possible 

 that in still larger colonies we may also here find developed secondary- hydrocladia, showing that a 

 primary hydrocladium can bear several secondary ones. 



The gonothecas are incompletely described both by Allman (1874 p. 477) and Broch (1903 

 p. 8) probably from imperfectly developed specimens. They are of very peculiar form (fig. XXXYII l>\. 

 They are attached by a stalk yvhich is not infrequently very short, almost rudimentary. The one 

 (adcauline) side is someyvhat flattened and short, the other however, highly curved and a good deal 

 longer, so that the plane of the aperture is almost or entirely parallel with the longitudinal axis of 



1 In fig. XXXVII<7, the secondary hvdrocladium shows only <>nc complete sarcothecal branch ithe basal i ; this is 

 due to the fact that the two next are broken off- Ordinarily, they appear in fully normal development at every single 



hydrotheea. 



