NO. 5 FRASER : HYDROIDS 285 



Plumularia mutabilis, new species 

 Plate 41, Fig. 50 



Trophosome. — Large colonies, up to 20 cm, grow in clusters ; the stem 

 is stout, without distinct nodes, not very much darker in color than the 

 light horn color hydrocladia. The arrangement of the hydrocladia varies 

 in different parts of the colony. Most commonly, they are regularly alter- 

 nate in the proximal portion, but strictly opposite in the distal portion. 

 The slender hydrocladia are much like the proximal hydrocladia of P. 

 adjecta, but the distal ones are not branched as they may be in that species. 

 The nodes here are well marked, flanked on each side by internodal septa. 

 The first internode is short, athecate; all the other internodes are longer, 

 and are thecate, but the first is not so long as the others. The hydrotheca 

 is placed much nearer the distal node. All the nematophores are small, the 

 pair of supracalycine nematophores reaching but little beyond the margin 

 of the hydrotheca. All the mesial nematophores are proximal to the hydro- 

 theca, 1 on the first thecate internode and 2 on each of the others ; there is 

 none on the proximal, athecate internode. There is a nematophore at the 

 base of the hydrocladial process ; when the hydrocladia are opposite, there 

 is a pair of opposite nematophores a short distance above the process; 

 when the hydrocladia are alternate, there is a nematophore nearly oppo- 

 site the process, but slightly below it. 



Gonosome. — Not observed. 



Distribution. — Station 1101-40, Agua Verde Bay, Gulf of California, 

 10 fathoms. 



Plumularia parva, new species 

 Plate 41, Fig. 51 



Trophosome. — Colony, very small and slender, 8 mm, grows singly 

 from a non-reticular stolon. The stem is slightly sinuous, unbranched, di- 

 vided into internodes of nearly the same length throughout, the nodes 

 distinctly marked. The hydrocladia are given off alternately, all in the 

 same plane, from short processes near the distal end of the internodes. 

 There is no short proximal internode ; the first one is thecate, the second, 

 athecate, and farther the thecate and athecate internodes alternate. The 

 athecate internodes are relatively long, sometimes almost as long as the 

 thecate; on the thecate internode, the hydrotheca is situated about two- 

 thirds of the way from the proximal node. The internodal septa are well 

 marked, 1 near each end of the internode. There is 1 mesial nematophore 

 to each internode, and a pair of supracalycine nematophores to each hydro- 



