NO. I FRASER : HYDROIDS 



117 



SO that the adcauline side is distinctly concave, and the abcauline, dis- 

 tinctly convex; or, the gonangium may be nearly straight and then 

 regularly obovate. The opening does not occupy all of the distal end. 



Plumularia tenuissima, new species 

 Plate 18, Fig. 10 



Trophosome. — Colonies growing from a stolon, somewhat loosely 

 clustered — 5 cm. Stem unbranched or very slightly and irregularly 

 branched, very slender, divided into long internodes without ridges; 

 each internode with a hydrocladium almost at its distal end, but the 

 hydrocladia are not always strictly alternate; nematophores numerous, 

 usually four to an internode besides the two that are on the hydrocladial 

 process. Hydrocladia long — up to 6 mm. — and very slender, bearing at 

 most four hydrothecae. Next to the hydrocladial process of the cauline 

 internode, there is a short internode, with two ridges but without hydro- 

 theca or nematophores ; next to this is a much longer internode, also with 

 a ridge near each end, with two nematophores but not bearing a hydro- 

 theca; the third internode is thecate, the hydrotheca being nearly 

 medially placed; it also has proximal and distal ridges, one, or some- 

 times two, mesial nematophores, below the hydrotheca, and two large 

 supracalycine nematophores; after this the nonthecate and the thecate 

 internodes follow in order, the former similar to the second and the 

 latter to the third internode. 



Gonosome. — Gonangia appear in some of the distal axils, on short 

 pedicels, slender, nearly tubular, 1.0 mm. long, 0.1 mm. in diameter, 

 smooth. 



