HYDROZOA 127 



over the fronds of seaweeds, often crossing and recrossing in a tangled 

 mass. At short intervals the upright, straight branches rise to one inch 

 or one and a half inches in height, and arc more or less branched. All 

 except the creeping stems are close set on each side, with cylindi-ical 

 zooid-cups which turn outward at the ends. The cups of the reproduc- 

 tive zooids are not sessile ; they are much larger than those of the nutri- 

 tive ones and are urn-shaped. (Plate XLII, A.) 



S. argentea. This is a beautiful species, common from New Jersey 

 northward. It has a profusion of silvery branches on a dark stem. The 

 colonies are often a foot or more long, and the branches at the top and 

 bottom of the stem are shorter and fewer than those in the middle of 

 the colony. The zooid-cups are nearly cylindrical, pressed closely to the 

 stem, nearly opposite or subalternate to one another, and end in 

 pointed tips. The medusa-bud is urn-shaped, with two horns at the top. 

 (Plate XLII, B.) 



S. cupressina, the sea-cypress. This species is similar to S. argentea, 

 but the main stem is thicker and longer, and the branches less crowded 

 and less subdivided. The branches are arched or drooping, instead of 

 straight, and gradually decrease in length at some distance from the 

 lower and upper parts of the stem, giving a spire-like apex, the stem 

 often continuing into a bare, branchless extremity. The zooid-cups are 

 tubular, not much narrowed or divergent above, and two-lipped on the 

 margin. It is found from New Jersey northward. (Plate XLII, B.) 



THE PLUMULARIANS 



These hydroids are feather-like in the manner of branching, 

 short lateral branches being arranged on each side of a long cen- 

 tral stem. In some species the stems are naked below and 

 resemble quills. The zooid-cups are only on one side of the 

 short branches. (Plate XLIIL) 



GENUS Aglaophemia 



A. struthioides, the ostrich-plume. This species, which is found on 

 the Pacific coast, is perhaps the most beautiful of the hydroids. It varies 

 in size and color, but always suggests a small ostrich-plume. The zooid- 

 cups are arranged in a single row on one side of each short branch, and 

 the main stem has a joint between each of the branches, which are 

 placed quite close together. The rims of the cups have sharp-pointed 

 teeth, and from the top emerge three tubular projections, which are 

 called nematophores, and are supposed to be degenerate zooids. At inter- 

 vals a branch is replaced by a cylindrical body covered with nemato- 

 phores, and in these the generative zooids are developed. (Plate XLIIL) 



GENUS Plumularia 



P.falcata (Johnston), or HydraUmania falcata (Hincks). This 

 species is found on shells and rocks near low-water mark from Long 



